Consolidate checking for msvc when generating debuginfo

Consolidate checking for msvc when generating debuginfo

If the target we're generating code for is msvc, then we do two main
things differently: we generate type names in a C++ style instead of a
Rust style and we generate debuginfo for enums differently.

I've refactored the code so that there is one function
(`cpp_like_debuginfo`) which determines if we should use the C++ style
of naming types and other debuginfo generation or the regular Rust one.