Delete RETURNTYPE and change how we get ReturnKind for gccover. (dotnet/coreclr#24600)

Delete RETURNTYPE and change how we get ReturnKind for gccover. (dotnet/coreclr#24600)

* Move GetReturnKindFromMethodTable to method.hpp.

We would need this in other places in the next commits.

* Delete unnecessary checks from callhelpers.

* Do not check return types in CanDeduplicateCode.

GC info v.2 has this information and it is checked in another place.

* Change ComPlusMethodFrame to use the new function.

* Change gccover.cpp to use GetReturnKindFromMethodTable.

* Delete RETURNTYPE.

* Add check to ComPlusMethodFrame.

* Delete check from threadsuspend.

codeInfo->GetCodeManager()->GetReturnKind(gcInfoToken) must always return a valid kind nowdays (it could return an invalid lind only when GC Info v2 was not available).

* Rename functions/arguments.

* Add check for IsValidReturnKind.

* delete unused var.

Commit migrated from https://github.com/dotnet/coreclr/commit/d5d18896900561b7aaf38ba9501a8525a4b9caea