Add k8s.cluster.uid fallback for GMP

[dashpole]

fixes #771

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.75%. Comparing base (4caace7) to head (832a421).
Report is 30 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #877      +/-   ##
==========================================
+ Coverage   61.03%   61.75%   +0.71%     
==========================================
  Files          56       58       +2     
  Lines        5903     6055     +152     
==========================================
+ Hits         3603     3739     +136     
- Misses       2143     2156      +13     
- Partials      157      160       +3     

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