fix: Long Stage names result in AnalysisRun creation failures during promotion

[aidan-canva]

Closes #3202

Long Stage names cause errors during promotions due to calculated labels (kargo.akuity.io/promotion) on AnalysisRun resources exceeding the max 63 character limit of a label value.

This solution moves the kargo.akuity.io/promotion label to an annotation which has a much larger max length. It doesn't appear this label key is used for selecting at the moment so its largely an informative value.

An alternative approach to truncate Stage name was considered (with hashing for uniqueness) but that greatly reduces legibility within the UI (IMO). Doing it inconsistently might work, but then impacts ability to debug and map relationships with resources easily.

This solution strikes a middle ground to unblock longer Stage names and give time for a more considered approach to naming/labeling conventions if its required.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 52.43%. Comparing base (e1d2fab) to head (bfd66c1).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3520      +/-   ##
==========================================
+ Coverage   52.27%   52.43%   +0.15%     
==========================================
  Files         290      294       +4     
  Lines       26330    26663     +333     
==========================================
+ Hits        13764    13980     +216     
- Misses      11814    11915     +101     
- Partials      752      768      +16     

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[krancour]

Tentatively assigned to v1.3.0, but might be a good candidate to be deferred.

[hiddeco]

I think docs/docs/50-user-guide/20-how-to-guides/60-verification.md contains a label example that has to be updated.

[aidan-canva]

Thanks @hiddeco, fixed!