Track ownerrefs between cluster-scoped and namespaced objects

[jcogilvie]

Fixes argoproj/argo-cd#24379

[codecov]

Codecov Report

❌ Patch coverage is 89.36170% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 47.82%. Comparing base (8849c3f) to head (a3fa709).
⚠️ Report is 59 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/cache/cluster.go	89.36%	3 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #774      +/-   ##
==========================================
- Coverage   54.26%   47.82%   -6.45%     
==========================================
  Files          64       64              
  Lines        6164     6622     +458     
==========================================
- Hits         3345     3167     -178     
- Misses       2549     3199     +650     
+ Partials      270      256      -14     

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[todaywasawesome]

Looks great, as was suggested in contrib meeting we should have an environmental variable. I think this should be disabled by default and only enabled when needed.

[jcogilvie]

I heard some other opinions in the contributor meeting. I agree with adding the escape hatch, but I'm not sure whether we should implement "conditional enable" or "emergency disable". Environment variable? App annotation? Other thoughts?

@crenshaw-dev had an opinion I know.

[sonarqubecloud]

Quality Gate passed

Issues
14 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
13.1% Duplication on New Code

See analysis details on SonarQube Cloud

[jcogilvie]

I went ahead with implementing this as a disable flag.

I did have an idea about a possible optimization, though it may change things a little more broadly than just buildGraph.

I was thinking if IterateHierarchyV2 were to always process the global/cluster-scoped (non-)namespace slice element last, we could keep track of missing refs that we hit along the way and resolve them all at once in a single go. Sound viable?