Stability on attributes and events

[jerbly]

For issue #564

Added warnings for missing stability on:

• Attributes
• Enum members in attributes
• Event AnyValues
• Enum members in AnyValues

[codecov]

Codecov Report

Attention: Patch coverage is 94.73684% with 2 lines in your changes missing coverage. Please review.

Project coverage is 74.8%. Comparing base (a11060e) to head (c1b5936).

Files with missing lines	Patch %	Lines
crates/weaver_semconv/src/group.rs	94.7%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #568     +/-   ##
=======================================
+ Coverage   74.5%   74.8%   +0.2%     
=======================================
  Files         51      51             
  Lines       3965    4003     +38     
=======================================
+ Hits        2957    2995     +38     
  Misses      1008    1008             

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[lquerel]

LGTM. Thank you so much!

[lmolkova]

Schema changes LGTM!