Improve performance of Enum.{Try}Parse (dotnet/coreclr#21214)

Improve performance of Enum.{Try}Parse (dotnet/coreclr#21214)

* Improve performance of Enum.{Try}Parse

In particular for the generic overloads, where this avoids all per-operation allocations when commonly used underlying types are used (for example, this improves when the underlying enum type is int but not double).

* Address PR feedback

Commit migrated from https://github.com/dotnet/coreclr/commit/88fb86f36d22c94cb5fc6424110bf3dac37ac83b