feat: Add func GetManagedObject

[cyrus-mc]

Retrieve object from cache based on ResourceKey. Cache manifest if it isn't already cached.

This is required in support of https://github.com/argoproj/argo-cd/issues/3854 and https://github.com/argoproj/argo-cd/pull/3863.

[sonarqubecloud[bot]]

Kudos, SonarCloud Quality Gate passed!

0 Bugs
0 Vulnerabilities (and 0 Security Hotspots to review)
0 Code Smells

No Coverage information
0.0% Duplication

[codecov[bot]]

Codecov Report

Merging #81 into master will decrease coverage by 0.26%. The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master      #81      +/-   ##
==========================================
- Coverage   52.52%   52.25%   -0.27%     
==========================================
  Files          25       25              
  Lines        2599     2612      +13     
==========================================
  Hits         1365     1365              
- Misses       1103     1116      +13     
  Partials      131      131              

Impacted Files	Coverage Δ
pkg/cache/cluster.go	52.06% <0.00%> (-1.52%)	:arrow_down:

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