Optimize DispatchProxyGenerator code path by using MetdataToken

[ViktorHofer]

See comment:

runtime/src/libraries/System.Reflection.DispatchProxy/src/System/Reflection/DispatchProxyGenerator.cs

Lines 834 to 836 in e8875e3

	// This assembly should work in netstandard1.3,
	// so we cannot use MemberInfo.MetadataToken here.
	// Therefore, it compares honestly referring ECMA-335 I.8.6.1.6 Signature Matching.

With #53283, we won't build a netstandard1.x configuration of this library anymore and the code path can be optimized. FWIW this could have already be done in the past via ifdef compiler directives.

cc @buyaa-n @joperezr @krwq @steveharter @jeffhandley

[FatTigerWang]

@ViktorHofer I will use MethodInfo.MetadataTokenn and MethodInfo.Module.Name to judge