OtlpHttpExporter concurrency and export condition improvements

[krynju]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 55 lines in your changes are missing coverage. Please review.

Project coverage is 0.00%. Comparing base (d68e343) to head (c0ada97).
Report is 1 commits behind head on master.

❗ Current head c0ada97 differs from pull request most recent head e3c6f89. Consider uploading reports for the commit e3c6f89 to get more accurate results

Files	Patch %	Lines
src/sdk/src/trace/span_processor.jl	0.00%	24 Missing ⚠️
src/sdk/src/exporter.jl	0.00%	22 Missing ⚠️
...oto/http/src/OpenTelemetryExporterOtlpProtoHttp.jl	0.00%	7 Missing ⚠️
src/sdk/src/log.jl	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #103       +/-   ##
==========================================
- Coverage   74.32%   0.00%   -74.33%     
==========================================
  Files          46      45        -1     
  Lines        1441    1368       -73     
==========================================
- Hits         1071       0     -1071     
- Misses        370    1368      +998     

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