x64 windows sourcehook hookmangen

[Kenzzer]

Add x64 dynamic hook support to SourceHook, Windows only

• Added x64GenContext to generate SourceHook virtual stubs on x86_64
• GenBuffer has been moved to sh_asm.h, since it's only ever used to allocate blocks of memories where assembly is written at
• x64JitWriter (inheriting from GenBuffer). It's a collection of helper functions to write x86_64 assembly bytes
• Added IGenContext in order to keep a single implementation of CHookManagerAutoGen that can be compiled on all architectures. Consequently, x64GenContext & GenContext inherit from IGenContext

This is already a massive PR as it is. And I really don't want to be adding Linux support right now, but it will come shortly after rest assured.

[Kenzzer]

@dvander @TheDS @peace-maker

I believe you'll be the ones that want to look most at this, given it's pertaining to sourcehook. My goal is to have this PR merged, before I make any further changes for linux support.