Add stability shields to markdown snippet generation

[jsuereth]

Adds stability shield and cleans up some formatting differences between weaver and current "head" build-tools.

• Partially wires in is_local vs. is_full logic.
• Add reusable stabiltiy shield method.
• Add stability to all necessary tables (metrics, enums + attributes)
• Update tests.

[codecov]

Codecov Report

Attention: Patch coverage is 70.83333% with 14 lines in your changes are missing coverage. Please review.

Project coverage is 63.6%. Comparing base (17ff1c6) to head (1deb55f).

❗ Current head 1deb55f differs from pull request most recent head 45cbf55. Consider uploading reports for the commit 45cbf55 to get more accurate results

Files	Patch %	Lines
crates/weaver_semconv_gen/src/gen.rs	68.8%	14 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main     #90     +/-   ##
=======================================
+ Coverage   63.4%   63.6%   +0.1%     
=======================================
  Files         54      54             
  Lines       3209    3235     +26     
=======================================
+ Hits        2037    2058     +21     
- Misses      1172    1177      +5     

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[lquerel]

LGTM