feat(tracing): allow to configure exporter by environment #1676

[vmarchaud]

Opening PR for feedback, see #1676 for discussions

Fixes #1676

[vmarchaud]

This is the first part to allow tracing SDKs to load exporter via environment, this will allows higher level SDKs that have exporters has dependencies to register them to be loaded via the environment (as discussed in SIG).
I exported the NoopSpanProcessor to be able to test which SpanProcessor is registered on the tracing SDK (since the exporter is configured through a span processor, we must first access the span processor and then the exporter)

[codecov]

Codecov Report

Merging #2100 (e7ed31f) into main (02239b5) will increase coverage by 0.02%.
The diff coverage is 95.00%.

@@            Coverage Diff             @@
##             main    #2100      +/-   ##
==========================================
+ Coverage   92.71%   92.73%   +0.02%     
==========================================
  Files         141      141              
  Lines        5037     5055      +18     
  Branches     1037     1042       +5     
==========================================
+ Hits         4670     4688      +18     
  Misses        367      367              

Impacted Files	Coverage Δ
...ckages/opentelemetry-core/src/utils/environment.ts	95.83% <ø> (ø)
...ntelemetry-tracing/src/export/NoopSpanProcessor.ts	71.42% <ø> (ø)
...s/opentelemetry-tracing/src/BasicTracerProvider.ts	96.10% <95.00%> (-0.51%)	⬇️
...emetry-core/src/platform/node/RandomIdGenerator.ts	87.50% <0.00%> (-6.25%)	⬇️

[Flarna]

A test which actually registers an exporter and uses it via env would be nice.

[vmarchaud]

A test which actually registers an exporter and uses it via env would be nice.

Added !

[obecny]

one concern with shutdown and some minor things

[obecny]

lgtm