[CONFIGURATION] File configuration - sdk resource

[marcalff]

Contributes to #2481

Remove restrictions on resource creation.

Changes

Please provide a brief description of the changes here.

• Remove restrictions on resource creation in the SDK.
• With declarative configuration, resources can be created after parsing a config.yaml file, calling a resource detector is no longer the only way to build a resource.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[netlify]

✅ Deploy Preview for opentelemetry-cpp-api-docs canceled.

Name	Link
🔨 Latest commit	e1c66bc
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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.02%. Comparing base (dbd0680) to head (e1c66bc).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3567      +/-   ##
==========================================
- Coverage   90.03%   90.02%   -0.00%     
==========================================
  Files         220      220              
  Lines        7065     7069       +4     
==========================================
+ Hits         6360     6363       +3     
- Misses        705      706       +1     

Files with missing lines	Coverage Δ
sdk/include/opentelemetry/sdk/resource/resource.h	100.00% <100.00%> (ø)
sdk/src/resource/resource.cc	96.78% <100.00%> (+0.48%)	⬆️

... and 1 file with indirect coverage changes

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[dbarker]

Looks good. Thanks!