Crossgen2 unable to find methods on MdArrays

[MichalStrehovsky]

using System;

int[,][,][,] x = new int[1, 1][,][,];

x[0, 0] = new int[123,2][,];
Console.WriteLine("Hello world", x[0,0]);

Compile with crossgen2. Notice that we hit a MissingMethodException at compile time and compiling Main is aborted.

This is because the reference to the MdArray Set method contains a bunch of EmbeddedSignatureData after #51764 and the signature doesn't match the synthetic method that the type system created.

I tried to see what CoreCLR is doing - it represents the array element type as ELEMENT_TYPE_VAR with index 0 and I assume magic happens somewhere. The managed type system doesn't do that.

This is a regression.

Related to #52444.

[mangod9]

@dotnet/crossgen-contrib @davidwrighton FYI

[davidwrighton]

Sigh. No good deed goes unpunished. And MDArray magic function lookup is special in yet another way.