chore: batch processor, aligning with latest spec changes for environments variables

[obecny]

Which problem is this PR solving?

• Fixes BatchProcessor #1905

Short description of the changes

• aligning the latest environment variables and config (names & defaults)
• changing the logic it works to handle correctly cases like dropping spans when limit is reached, batch size, time to export, schedule time for next export etc.

[dyladan]

The name of the PR is not a great description of the changes. Since it is how the changelog is generated I think we should have descriptive names.

[codecov]

Codecov Report

Merging #1918 (ad33d65) into main (06c7ec7) will decrease coverage by 0.27%.
The diff coverage is 93.61%.

@@            Coverage Diff             @@
##             main    #1918      +/-   ##
==========================================
- Coverage   92.78%   92.51%   -0.28%     
==========================================
  Files         182      178       -4     
  Lines        6366     6063     -303     
  Branches     1342     1291      -51     
==========================================
- Hits         5907     5609     -298     
+ Misses        459      454       -5     

Impacted Files	Coverage Δ
...ckages/opentelemetry-core/src/utils/environment.ts	90.00% <ø> (ø)
...telemetry-tracing/src/export/BatchSpanProcessor.ts	91.20% <93.61%> (+0.29%)	⬆️
...s/opentelemetry-instrumentation-fetch/src/fetch.ts
...-instrumentation-fetch/src/enums/AttributeNames.ts
...emetry-instrumentation-xml-http-request/src/xhr.ts
...mentation-xml-http-request/src/enums/EventNames.ts