Add stability level info on generated metrics' documentation

[ChrsMark]

Description

This PR exposes the stability level of metrics to their generated documentation. This allows us for defining different stability levels for metrics that a components emits. In the future once a component is stable it should be able to introduce new metrics with lower stability levels for experimental/development reasons.

Related to #13297 and #11878. One prior attempt was #5487.

My proposal here is:

1. expose the stability in the docs conditionally, (if it exists add it)
2. (in follow-up PR) If no stability is defined add development by default
3. (in follow-up PR) Update the Collector contrib components using the above
4. (in follow-up PR) Consider making the stability a required attribute in the metadata-schema

Link to tracking issue

Fixes #13748

Testing

Tuned

Documentation

Sample generated documentation:

Unit	Metric Type	Value Type	Monotonic	Stability
By	Sum	Int	true	stable

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.43%. Comparing base (66f2c45) to head (9a56ddc).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #13756   +/-   ##
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  Coverage   91.43%   91.43%           
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  Files         640      640           
  Lines       42665    42665           
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  Hits        39009    39009           
  Misses       2836     2836           
  Partials      820      820           

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[dmitryax]

@ChrsMark why did we chose to make the stability a group with level option instead of flat stability: development

My concern is that it's too verbose and I see that the weaver v2 schema has it flat.

[ChrsMark]

@ChrsMark why did we chose to make the stability a group with level option instead of flat stability: development

My concern is that it's too verbose and I see that the weaver v2 schema has it flat.

The current PR didn't add the Stability struct but only made use of it in the templates so as the information is exposed to the docs. This was originally added at #11160.

[dmitryax]

@ChrsMark I see. It was added a year ago... Thanks for clarifying