fix: don't let PeriodicExportingMetricReader block process exit

[seemk]

PeriodicExportingMetricReader currently keeps the Node.js process from exiting when not doing an explicit shutdown.

[codecov]

Codecov Report

Merging #3106 (50abeae) into main (1a0e0c4) will decrease coverage by 1.09%.
The diff coverage is n/a.

❗ Current head 50abeae differs from pull request most recent head 35499ec. Consider uploading reports for the commit 35499ec to get more accurate results

@@            Coverage Diff             @@
##             main    #3106      +/-   ##
==========================================
- Coverage   93.08%   91.98%   -1.10%     
==========================================
  Files         188       82     -106     
  Lines        6243     2407    -3836     
  Branches     1313      522     -791     
==========================================
- Hits         5811     2214    -3597     
+ Misses        432      193     -239     

Impacted Files	Coverage Δ
packages/opentelemetry-resources/karma.worker.js	0.00% <0.00%> (-100.00%)	⬇️
...s/opentelemetry-core/src/platform/node/sdk-info.ts	0.00% <0.00%> (-100.00%)	⬇️
...opentelemetry-core/src/platform/node/globalThis.ts	0.00% <0.00%> (-100.00%)	⬇️
...pentelemetry-core/src/platform/node/performance.ts	0.00% <0.00%> (-100.00%)	⬇️
...emetry-api-metrics/src/platform/node/globalThis.ts	0.00% <0.00%> (-100.00%)	⬇️
...lemetry-resources/src/detectors/ProcessDetector.ts	31.81% <0.00%> (-68.19%)	⬇️
...perimental/packages/otlp-exporter-base/src/util.ts	79.41% <0.00%> (-17.65%)	⬇️
...ckages/opentelemetry-exporter-zipkin/src/zipkin.ts	84.48% <0.00%> (-15.52%)	⬇️
...lemetry-resources/src/detectors/BrowserDetector.ts	93.33% <0.00%> (-6.67%)	⬇️
...s-base/src/export/PeriodicExportingMetricReader.ts
... and 105 more

[pichlermarc]

Looks great. Thanks for adding this! 🙂