Add NetCoreAppCurrent config to where it's missing (#54215)

Add NetCoreAppCurrent config to where it's missing (#54215)

* Add NetCoreAppCurrent config to where it's missing

This is addressing the following scenarios in order:
- When there is a netcoreapp3.1 or net5.0 asset available in the lib,
  also add a NetCoreAppCurrent configuration to avoid PackageReferences
  to libraries that are inbox in net6.0 but not in previous .NetCoreApp
  versions. Examples are M.Win32.Registry which will be inbox soon.
- When there's a NetCoreAppCurrent config in the lib but not in the ref,
  add it there as well to always resolve the ref of the current version.
- When there are NetCoreAppCurrent rid specific configuration in the lib
  not a non-rid configuration, add one so that P2Ps from rid-less
  NetCoreAppCurrent configs in other projects, pick the
  NetCoreAppCurrent config from the lib and the ref.