[NativeAOT-LLVM] Implement generic `IDynamicInterfaceCastable`

[SingleAccretion]

See https://github.com/dotnet/runtime/pull/108235, which uses the thunk pool and will not work for us.

Rough idea: 1) Produce fat function pointers in interface resolve. 2) Teach interface call lowering fat function pointer dispatch. 3) Limit the impact of this on code quality by:

• Recording all the IDIC-implementing interfaces during scanning.
• Only using the fat function pointer aware lowering for calls to interfaces that the IDIC implementations implement. So if for example we have [IDICImpl] IImplOne : ISomething, [IDICImpl] IImplTwo : ISomething during scanning, the final set of affected methods would be those on ISomething and IImplOne with IImplTwo, since the latter "implement themselves".

[jkotas]

I think it would be fine to not support this feature for wasm AOT until it is needed for something real.