Jaeger: ThriftSender unit test

[esigo]

Adds unit test to cover the memory leak issue reported in #1160

Changes

Mocks Transport so that we can reach ThriftSender::Append when JaegerExporter::Export was called.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #1162 (11eee93) into main (09fb4e0) will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1162      +/-   ##
==========================================
+ Coverage   93.25%   93.26%   +0.02%     
==========================================
  Files         173      173              
  Lines        6362     6362              
==========================================
+ Hits         5932     5933       +1     
+ Misses        430      429       -1     

Impacted Files	Coverage Δ
...include/opentelemetry/sdk/common/circular_buffer.h	100.00% <0.00%> (+2.09%)	⬆️

[lalitb]

LGTM. Shouldn't this be successful now that #1160 is merged? cc @bjosv

[esigo]

LGTM. Shouldn't this be successful now that #1160 is merged? cc @bjosv

Seems there was a timeout in batch_span_processor_test:
//sdk/test/trace:batch_span_processor_test TIMEOUT in 300.1s

[bjosv]

LGTM! Sorry for late response.