support for generic (static) methods, thus also support for extension…

[dogguts]

this PR provides support for generic methods (as (among others) requested in #386 ), and thus also for generic extension methods.
An actual use case for this whould be the, in EF Core 5.0, introduced "Collate" extension method, wich has a generic signatue:

// https://github.com/dotnet/efcore/blob/v5.0.7/src/EFCore.Relational/Extensions/RelationalDbFunctionsExtensions.cs 
public static TProperty Collate<TProperty>(
           [NotNull] this DbFunctions _,
           [NotNull] TProperty operand,
           [NotNull] [NotParameterized] string collation)

Also contains additional unit tests

[Nokecy]

Is this PR reviewed? @StefH

[StefH]

Not yet.

I'll do it.

Thanks for this PR.

[Nokecy]

@dogguts Can you please resolve merge conflicts?

[dogguts]

resolved 😄

[Nokecy]

@StefH 😄