Add CreateDelegatePointer for PROC and FARPROC

Is your feature request related to a problem? Please describe.

For now, we have CreateDelegate to create delegate from PROC and FARPROC. But when the delegate has generated to a struct for delegate*, it cannot work.

Describe the solution you'd like

Add a CreateDelegatePointer method for PROC and FARPROC, such as:

[MethodImpl(MethodImplOptions.AggressiveInlining)]
internal TDelegate CreateDelegatePointer<TDelegate>() where T : unmanaged => Unsafe.As<PROC, T>(ref this.Value);

Describe alternatives you've considered

For now, we can create an extension to use it:

JClass mainClass = env->functions->FindClass.CreateDelegatePointer<FindClass>().Value(env, "java/lang/String"u8.AsPCSTR());

file static class Extensions
{
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static PCSTR AsPCSTR(this scoped in ReadOnlySpan<byte> data) => Unsafe.As<ReadOnlySpan<byte>, PCSTR>(ref Unsafe.AsRef(in data));

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static TDelegate CreateDelegatePointer<TDelegate>(this PROC function) where T : unmanaged => Unsafe.As<PROC, T>(ref function);
}

Additional context
#1629

Locate the existing CreateDelegate implementations for PROC and FARPROC and inspect how their supporting types are generated. Add the corresponding pointer-delegate entry points, then verify the delegate* struct scenario described in the issue and the existing usage pattern from #1629.