[C#] Fix building with deprecated=no

[Drako]

This fixes GH-84426.

I added the option --no-deprecated to build_assemblies.py, which needs to be used, if the editor was built with deprecated=no module_mono_enabled=yes.

This conditionally disables code in Compat.cs which references deprecated classes or functions.

[akien-mga]

Makes sense to me. I'm not too familiar with C# buildsystem stuff though so I'll let @raulsntos double check.

[AThousandShips]

You used a merge commit to update your branch, please use rebase in the future instead, see here

You will need to squash your commits before this can be merged (though that can wait until the team has reviewed), see here

But make sure not to use merge commits in the future

[Drako]

I don't see any merge commits ;)

[raulsntos]

Makes sense to me, but we'd want to disable the entire Compat.cs and also do the same in the GodotSharpEditor assembly.

[Drako]

Makes sense to me. I also considered excluding Compat.cs first, but wasn't sure, if there was stuff in it which is still needed.
Anyway I conditionally excluded both Compat.cs files now and it seems to be working so far.

[raulsntos]

Looks good to me, thanks!

[akien-mga]

Thanks! And congrats for your first merged Godot contribution 🎉