out_opentelemetry: enhance logs handling with groups and metadata sup…

…port

The following patch introduce a big change on how the plugin now process the logs
with OTLP format, the high-level features are:

1. Full metadata support:
  - with the new changes in in_opentelemetry, there is no metadata loss

2. Proper encoding of non-OTLP records as OTLP
  - The plugin is flexible enough to encode any type of log record.

At a low level, we re-architect how resource logs, resource, span_logs, scope and
logs are handled. All of this has been implemented on top of the new Fluent Bit
groups support for logs.

Use cases tested:

 - OTel Collector (gRPC) --> Fluent Bit --> OTel Collector (gRPC)
 - dummy, tail, forward  --> Fluent Bit --> OTel Collector (gRPC)

Signed-off-by: Eduardo Silva <[email protected]>

plugins/out_opentelemetry/CMakeLists.txt

@@ -1,6 +1,8 @@
-set(src
-  opentelemetry.c
-  opentelemetry_conf.c
-  )
-
-FLB_PLUGIN(out_opentelemetry "${src}" "")
+set(src
+  opentelemetry.c
+  opentelemetry_logs.c
+  opentelemetry_utils.c
+  opentelemetry_conf.c
+  )
+
+FLB_PLUGIN(out_opentelemetry "${src}" "")