fix(configuration): percent-decode keys and values in resource.attributes_list

[MikeGoldsmith]

Which problem is this PR solving?

The OTel resource spec says that , and = in OTEL_RESOURCE_ATTRIBUTES keys and values MUST be percent-encoded, and other characters MAY be percent-encoded. The configuration schema for resource.attributes_list uses the same format. The current parsing in mergeAttributesList ignores percent-encoding.

Spec: https://opentelemetry.io/docs/specs/otel/resource/sdk/#specifying-resource-information-via-an-environment-variable

Short description of the changes

Update mergeAttributesList in FileConfigFactory:

• Split each entry by = and require exactly two parts (an unencoded = in a value means the entry is invalid per spec)
• Percent-decode key and value with decodeURIComponent
• On any parse or decode error, discard the entire attributes_list and emit a diag.warn (matches the spec's "on error, discard all" rule, and matches the existing EnvDetector in the opentelemetry-resources package)

Adds three fixtures + tests:

• valid percent-encoded (%2C, %3D, %C3%A9)
• invalid percent-sequence (%ZZ)
• unencoded = in value

Type of change

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

How Has This Been Tested?

• 85 configuration package tests pass (3 new)
• Full lint passes

Closes #6769

[codecov]

Codecov Report

❌ Patch coverage is 90.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.94%. Comparing base (55606c3) to head (ecf8baf).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...al/packages/configuration/src/FileConfigFactory.ts	90.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6787      +/-   ##
==========================================
- Coverage   94.96%   94.94%   -0.02%     
==========================================
  Files         380      380              
  Lines       12897    12910      +13     
  Branches     2937     2939       +2     
==========================================
+ Hits        12247    12258      +11     
- Misses        650      652       +2     

Files with missing lines	Coverage Δ
...al/packages/configuration/src/FileConfigFactory.ts	96.72% <90.00%> (-1.45%)	⬇️

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