fix: remove runtime references from codegen [MTT-4088]

[ShadauxCat]

This changes the method by which we look up types in codegen from looking it up based on the actual type to looking them up based on type names. It removes the dependencies on runtime assemblies from the codegen assembly.

This comes from the ILPP team and has a few bits of logic behind it:

1. There's currently a bug in ILPP that's causing it to crash when running against certain platforms on certain hosts (e.g., webgl on mac) if collectibles is referenced
2. There's a chicken and egg problem of having to load Unity.Netcode.Runtime in order to know how to modify Unity.Netcode.Runtime
3. Most significantly, when writing to a webgl assembly, the ILPP process loads the runtime assembly, which means if there are differences between the two (such as with collections, which excludes AtomicSafetyHandle in player builds) this results in IL being generated based on the editor definition of the class instead of the player definition, which can result in IL code

The immediate benefit of this is working around the aforementioned crash, which is also being fixed by the ILPP team. This will fix it on all of our supported platforms (whereas the fix by the ILPP will only hit 2020.3, 2021.3, and 2022.x)

The long-term benefit is that this switches us to a mode of following best practices and avoids running into any other such issues in the future. The way we were doing it worked (aside from the crash) but this is the "right way" to do it.

Changelog

• Fixed: Building for webgl on MacOS (and some other platform combinations) no longer results in a TypeLoadException

Testing and Documentation

• No tests have been added.
• No documentation changes or additions were necessary.

[ShadauxCat]

Guess this is more of a fix than a chore...

[0xFA11]

rather than hardcoding all string by hand here, we could still reference Netcode.Runtime's types but instead of typeof(XXX) type-based lookup in the ILPP/Cecil code, we could simply produce strings here with nameof(XXX) to keep it consistent with the Netcode.Runtime — also by doing that, we keep Netcode.Runtime reference around and we don't need to have Unity.Netcode.Shared asmdef and/or duplicate xxHash implementation, we could simply revert them back to current state.

[0xFA11]

this could be the bug we're looking for (ILPP failing to make RpcExecStage protected from internal)

[jeffreyrainy]

How does adding a few string prevents the change from protected to internal ? (Not arguing it doesn't, just really curious how one leads to the other)

[0xFA11]

more specifically, this part: viour/__RpcExecSt

[0xFA11]

superseded by #2199