Explore test/code coverage to identify test improvements

[rmccorm4]

To automate identifying which modules and objects are missing testing, we can try some tools like tarpaulin or cargo-llvm-cov

Doesn't necessarily have to be added in automation or enforce any minimum code coverage requirements - but can at least help identify areas for test improvement short term.

Depending on how heavy it is, we can add it to rust pre merge action or a nighty job.

[tanmayv25]

Following is the code coverage of rust runtime as of 2/11/25:

Filename                                      Regions    Missed Regions     Cover   Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
component.rs                                       32                32     0.00%          24                24     0.00%          74                74     0.00%           0                 0         -
component/client.rs                                86                86     0.00%          17                17     0.00%         149               149     0.00%           0                 0         -
component/endpoint.rs                              43                43     0.00%           9                 9     0.00%          70                70     0.00%           0                 0         -
component/registry.rs                               2                 2     0.00%           2                 2     0.00%           8                 8     0.00%           0                 0         -
component/service.rs                               34                34     0.00%           8                 8     0.00%          45                45     0.00%           0                 0         -
config.rs                                          29                18    37.93%          10                 5    50.00%          55                24    56.36%           0                 0         -
discovery.rs                                        5                 5     0.00%           4                 4     0.00%          13                13     0.00%           0                 0         -
distributed.rs                                     53                53     0.00%          19                19     0.00%          88                88     0.00%           0                 0         -
engine.rs                                           7                 3    57.14%           7                 3    57.14%          29                14    51.72%           0                 0         -
pipeline.rs                                         3                 2    33.33%           3                 2    33.33%           9                 6    33.33%           0                 0         -
pipeline/context.rs                                85                34    60.00%          62                27    56.45%         261                89    65.90%           0                 0         -
pipeline/error.rs                                   5                 4    20.00%           2                 1    50.00%           8                 5    37.50%           0                 0         -
pipeline/network.rs                                47                32    31.91%          18                12    33.33%          70                47    32.86%           0                 0         -
pipeline/network/codec/two_part.rs                159                27    83.02%          38                 4    89.47%         721                31    95.70%           0                 0         -
pipeline/network/egress/push.rs                    33                33     0.00%           7                 7     0.00%          89                89     0.00%           0                 0         -
pipeline/network/ingress/push_endpoint.rs          35                35     0.00%           5                 5     0.00%          33                33     0.00%           0                 0         -
pipeline/network/ingress/push_handler.rs           59                59     0.00%           3                 3     0.00%          61                61     0.00%           0                 0         -
pipeline/network/tcp.rs                            27                 2    92.59%           5                 1    80.00%         174                 5    97.13%           0                 0         -
pipeline/network/tcp/client.rs                     71                35    50.70%          11                 5    54.55%         126                46    63.49%           0                 0         -
pipeline/network/tcp/server.rs                    203                95    53.20%          33                13    60.61%         323               119    63.16%           0                 0         -
pipeline/nodes.rs                                  61                15    75.41%          29                 6    79.31%         100                15    85.00%           0                 0         -
pipeline/nodes/sinks/base.rs                       13                 3    76.92%           5                 1    80.00%          20                 1    95.00%           0                 0         -
pipeline/nodes/sinks/pipeline.rs                   13                 1    92.31%           6                 0   100.00%          18                 0   100.00%           0                 0         -
pipeline/nodes/sinks/segment.rs                    19                 3    84.21%           9                 1    88.89%          32                 1    96.88%           0                 0         -
pipeline/nodes/sources/base.rs                     50                13    74.00%          15                 5    66.67%         105                11    89.52%           0                 0         -
pipeline/nodes/sources/common.rs                   24                 6    75.00%          10                 2    80.00%          49                 6    87.76%           0                 0         -
pipeline/registry.rs                               38                 6    84.21%          16                 4    75.00%          95                20    78.95%           0                 0         -
protocols.rs                                        1                 1     0.00%           1                 1     0.00%           3                 3     0.00%           0                 0         -
protocols/annotated.rs                             37                37     0.00%          14                14     0.00%          87                87     0.00%           0                 0         -
runtime.rs                                         36                25    30.56%          12                 7    41.67%          56                28    50.00%           0                 0         -
service.rs                                         32                25    21.88%          12                 8    33.33%         102                46    54.90%           0                 0         -
transports/etcd.rs                                 93                93     0.00%          27                27     0.00%         158               158     0.00%           0                 0         -
transports/etcd/lease.rs                           60                60     0.00%           6                 6     0.00%          69                69     0.00%           0                 0         -
transports/nats.rs                                112                78    30.36%          26                18    30.77%         152                79    48.03%           0                 0         -
transports/nats/slug.rs                            33                33     0.00%          15                15     0.00%          73                73     0.00%           0                 0         -
worker.rs                                          86                34    60.47%          15                 6    60.00%         114                33    71.05%           0                 0         -
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                                            1726              1067    38.18%         505               292    42.18%        3639              1646    54.77%           0                 0         -