Remove ByValueMarshalKindSupport.Unnecessary and move ByValueContentsMarshalKindValidator to analyzers only#125458

Copilot wants to merge 4 commits intomaindotnet/runtime:mainfrom

copilot/move-byvaluecontentsmarshalkindvalidatordotnet/runtime:copilot/move-byvaluecontentsmarshalkindvalidatorCopy head branch name to clipboard