Clean up after apimachinery dep deletion

[monopole]

The work leading up to #2506, and the residue of a previous approach to kubectl integration, resulted in interfaces and implementations of those interfaces that are no longer needed now that #2506 is closed.

Things to delete (maybe not a complete list)

• interfaces
  • ifc.Kunstructured
  • ifc.Validator
  • resource.ConflictDetector
• everything in packages
  • api/wrappy (push WNode functionality down into RNode)
  • api/provider
• misc stuff
  • use of FlagEnableKyamlDefaultValue
  • use of IfApiMachineryElseKyaml (see Eliminate checking FlagEnableKyamlDefaultValue in tests #3304)

This makes Resource a direct wrapper to RNode.

Longer term (file a new issue?), get rid of Resource.

Its only purpose was to hold ancillary, transient data about the resource being transformer, like its original (non-prefixed) name. Such things are now tracked in metadata annotations inside RNode.