Move Native Library APIs to NativeLibrary class (#21821)

Move Native Library APIs to NativeLibrary class (#21821)

Move APIs that manipulate native libraries from
System.Runtime.InteropServices.Marshal class to the new
System.Runtime.InteropServices.NativeLibrary class.

In API review: #32015,
The LoadLibrary APIs were originally Approved to live in
System.Runtime.InteropServices.Marshal class.

However, recently the decision was changed such that the APIs are
in a new NativeLibrary class.