[Dvaas]: Add library that allows DVaaS/Arriba to process user-provided test vectors using a bare-bones, but sane API.

[VSuryaprasad-HCL]

Keyword Check:

~/pins_upstream/sonic-buildimage/src/sonic-p4rt/sonic-pins/dvaas$ ~/tools/keyword_checks.sh .
Keyword check Passed.

Build result:

sonic/src/sonic-p4rt/sonic-pins$ bazel build $BAZEL_BUILD_OPTS ...
INFO: Analyzed 579 targets (0 packages loaded, 0 targets configured).
INFO: Found 579 targets...
INFO: Elapsed time: 23.757s, Critical Path: 20.22s
INFO: 6 processes: 2 internal, 4 linux-sandbox.
INFO: Build completed successfully, 6 total actions

Test result:

/sonic/src/sonic-p4rt/sonic-pins$ bazel test $BAZEL_BUILD_OPTS --cache_test_results=no ...
INFO: Analyzed 579 targets (0 packages loaded, 4 targets configured).
INFO: Found 389 targets and 190 test targets...
INFO: Elapsed time: 215.377s, Critical Path: 124.17s
INFO: 244 processes: 287 linux-sandbox, 18 local.
INFO: Build completed successfully, 244 total actions
//dvaas:port_id_map_test                                                 PASSED in 0.6s
//dvaas:test_vector_stats_diff_test                                      PASSED in 0.1s
//dvaas:test_vector_stats_test                                           PASSED in 2.2s
//dvaas:test_vector_test                                                 PASSED in 0.6s
//gutil:collections_test                                                 PASSED in 0.5s
//gutil:io_test                                                          PASSED in 0.6s
//gutil:proto_matchers_test                                              PASSED in 1.0s
//thinkit:generic_testbed_test                                           PASSED in 1.6s
//thinkit:mock_control_device_test                                       PASSED in 1.6s
//thinkit:mock_generic_testbed_test                                      PASSED in 2.9s
//thinkit:mock_mirror_testbed_test                                       PASSED in 0.7s
//thinkit:mock_ssh_client_test                                           PASSED in 0.0s
//thinkit:mock_switch_test                                               PASSED in 3.3s
//thinkit:mock_test_environment_test                                     PASSED in 0.3s
//thinkit:switch_test                                                    PASSED in 0.8s
//sai_p4/instantiations/google/tests:p4_constraints_integration_test     PASSED in 2.3s
  Stats over 5 runs: max = 2.3s, min = 0.7s, avg = 1.1s, dev = 0.6s
//sai_p4/instantiations/google/test_tools:table_entry_generator_test     PASSED in 44.1s
  Stats over 50 runs: max = 44.1s, min = 0.8s, avg = 3.5s, dev = 10.2s

Executed 190 out of 190 tests: 190 tests pass.
INFO: Build completed successfully, 244 total actions