add support for OTEL_SERVICE_NAME environment variable

[tsloughter]

No description provided.

[codecov]

Codecov Report

Merging #302 (97f8106) into main (2b6a188) will increase coverage by 0.07%.
The diff coverage is 92.85%.

@@            Coverage Diff             @@
##             main     #302      +/-   ##
==========================================
+ Coverage   37.27%   37.35%   +0.07%     
==========================================
  Files          46       46              
  Lines        3262     3266       +4     
==========================================
+ Hits         1216     1220       +4     
  Misses       2046     2046              

Flag	Coverage Δ
api	65.14% <100.00%> (ø)
elixir	14.41% <0.00%> (ø)
erlang	37.35% <92.85%> (+0.07%)	⬆️
exporter	19.75% <ø> (ø)
sdk	76.74% <92.30%> (+0.16%)	⬆️

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Impacted Files	Coverage Δ
apps/opentelemetry/src/otel_resource_detector.erl	91.89% <92.30%> (+0.46%)	⬆️
...pps/opentelemetry_api/src/otel_tracer_provider.erl	81.25% <100.00%> (ø)

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