[v3] Add render generator

[yuwenma]

Related: #5673

Description
Generator reads the schema Render.Generate and parses the raw and kustomize resources based on render.generate.manifests.

[codecov]

Codecov Report

Merging #5865 (c7bd42e) into master (7a2ba77) will increase coverage by 0.02%.
The diff coverage is 77.77%.

@@            Coverage Diff             @@
##           master    #5865      +/-   ##
==========================================
+ Coverage   70.80%   70.82%   +0.02%     
==========================================
  Files         446      447       +1     
  Lines       16816    16869      +53     
==========================================
+ Hits        11906    11947      +41     
- Misses       4024     4031       +7     
- Partials      886      891       +5     

Impacted Files	Coverage Δ
pkg/skaffold/deploy/kustomize/util.go	88.23% <ø> (ø)
pkg/skaffold/render/generate/generate.go	77.35% <77.35%> (ø)
pkg/skaffold/deploy/kustomize/kustomize.go	74.07% <100.00%> (ø)

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