fix: ensure cloud monitoring exporter checks for metric descriptors before creating them

[leonardopliski]

Changes:

• Fixes cloud-monitoring-exporter tries to create time series metric descriptors on every application bootstrap #528.
• Checks for the metric descriptor existence before creating a new one, as @dashpole mentioned in the Go SDK code;
• Added tests;

[codecov]

Codecov Report

Merging #533 (d4b458c) into main (d5f34a3) will increase coverage by 0.06%.
The diff coverage is 100.00%.

❗ Current head d4b458c differs from pull request most recent head bf03520. Consider uploading reports for the commit bf03520 to get more accurate results

@@            Coverage Diff             @@
##             main     #533      +/-   ##
==========================================
+ Coverage   95.99%   96.05%   +0.06%     
==========================================
  Files          18       18              
  Lines         649      659      +10     
  Branches      118      119       +1     
==========================================
+ Hits          623      633      +10     
  Misses         26       26              

Impacted Files	Coverage Δ
...emetry-cloud-monitoring-exporter/src/monitoring.ts	95.65% <100.00%> (+0.41%)	⬆️
...entelemetry-cloud-monitoring-exporter/src/utils.ts	100.00% <100.00%> (ø)

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[aabmass]

Just a few comments otherwise LGTM :)

[aabmass]

/gcbrun

[aabmass]

Thanks for the PR!

[aabmass]

@leonardopliski could you address the header-check and conventional commits CI (the PR title should follow conventional commits)

[leonardopliski]

header

Sure, on it @aabmass

[leonardopliski]

@leonardopliski could you address the header-check and conventional commits CI (the PR title should follow conventional commits)

Done @aabmass, should be good go to now

[aabmass]

/gcbrun