refactor(otlp-exporter-base): use get*FromEnv() for otlp exporter config

[weyert]

Which problem is this PR solving?

Migrated away from using process.env to use the getStringFromEnv-function

Fixes #5562

Short description of the changes

Replaced the usage of process.env with the built-in getEnv utility functions

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Test A

Checklist:

• Followed the style guidelines of this project
• Unit tests have been added
• Documentation has been updated

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.07%. Comparing base (2d37608) to head (2137244).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5583      +/-   ##
==========================================
- Coverage   95.07%   95.07%   -0.01%     
==========================================
  Files         308      308              
  Lines        8039     8037       -2     
  Branches     1627     1626       -1     
==========================================
- Hits         7643     7641       -2     
  Misses        396      396              

Files with missing lines	Coverage Δ
...base/src/configuration/shared-env-configuration.ts	100.00% <100.00%> (ø)

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[pichlermarc]

I took the liberty to address the remaining comments and resolve conflicts. This should be good to merge now.

requested changes were addressed.