feat(configuration): refactoring config loader to print warning message

[maxday]

Part Of #6107

While I wanted to add some simple debug logs, I noticed that it might require a bigger change.
I started small with only two env variables OTEL_TRACES_SAMPLER and OTEL_TRACES_SAMPLER_ARG to make sure we all agree on the approach.

The new approach for loading the config (and adding warning logs) is the following:

1. Have a map of env variable + possible values
2. The env reading happens only one time (it will auto-loop over all defined env variables)
3. Since we now know the list of allowed values, it can print generic warning message without any additional work

Note that everything is strongly typed, I just did String for now, but it can be super easily extended to Bool, Number and StringList. I also added unit test around new functions.

Very open to any feedback, my plan was to start small to validate the approach, and if you like it, I can do follow-up PRs to adopt this mechanism in all the EnvironmentConfigFactory.ts

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

Checklist:

• Followed the style guidelines of this project
• Unit tests have been added
• [N/A] Documentation has been updated

Output of local unit test running

  EnvReader
    readEnvVar
      ✔ should return undefined when env var is not set
      ✔ should return the value when env var is set
      ✔ should return defaultValue when env var is not set and defaultValue is provided
      ✔ should return the value when it matches allowedValues
      ✔ should warn and return undefined for invalid value with no defaultValue
      ✔ should warn and return defaultValue for invalid value with defaultValue
      ✔ should not warn when no allowedValues is defined
    readAllEnvVars
      ✔ should read OTEL_TRACES_SAMPLER when set to a valid value

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.73%. Comparing base (e9831e7) to head (06c5d63).
⚠️ Report is 29 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6524      +/-   ##
==========================================
- Coverage   95.75%   95.73%   -0.02%     
==========================================
  Files         364      366       +2     
  Lines       12096    12138      +42     
  Branches     2885     2893       +8     
==========================================
+ Hits        11582    11620      +38     
- Misses        514      518       +4     

Files with missing lines	Coverage Δ
...mental/packages/configuration/src/EnvDefinition.ts	100.00% <100.00%> (ø)
...perimental/packages/configuration/src/EnvReader.ts	100.00% <100.00%> (ø)
...ages/configuration/src/EnvironmentConfigFactory.ts	99.12% <100.00%> (-0.44%)	⬇️

... and 1 file with indirect coverage changes

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[maryliag]

Thank you for working on this
LGTM

[maryliag]

Btw, I updated the PR description to say "Part Of" instead of "Fixes", since this PR is just the start and not the complete solution for that issue