feat(sdk-logs)!: do not read environment variables from window

[pichlermarc]

Which problem is this PR solving?

Migrates from getEnv() to using the new get*FromEnv() methods added in #5443. Also inlines the defaults. This drops
"env var configuration" (via window.OTEL_* ) in browser environments. As such I had to move some tests to different places to ensure they only run in the correct context.

This breaking change now will enable us to split the env var config code completely in a non-breaking feature release later.

Refs #5217

Type of change

• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How Has This Been Tested?

• Unit tests

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.91%. Comparing base (3c65b56) to head (f8d5eca).
Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5472   +/-   ##
=======================================
  Coverage   94.91%   94.91%           
=======================================
  Files         308      308           
  Lines        7981     7992   +11     
  Branches     1682     1693   +11     
=======================================
+ Hits         7575     7586   +11     
  Misses        406      406           

Files with missing lines	Coverage Δ
experimental/packages/sdk-logs/src/config.ts	100.00% <100.00%> (ø)
...sdk-logs/src/export/BatchLogRecordProcessorBase.ts	93.61% <100.00%> (+0.67%)	⬆️

[trentm]

I'll trust you on the Karma/browser-test changes. I haven't learned what Karma is doing.