Pica/Math: Improved the design of the Vec2/Vec3/Vec4 classes and simplified rasterizer code accordingly.

- Swizzlers now return const objects so that things like "first_vec4.xyz() = some_vec3" now will fail to compile (ideally we should support some vector holding references to make this actually work).
- The methods "InsertBeforeX/Y/Z" and "Append" have been replaced by more versions of MakeVec, which now also supports building new vectors from vectors.
- Vector library now follows C++ type promotion rules (hence, the result of Vec2<u8> with another Vec2<u8> is now a Vec2<int>).

Pica/citra-qt: Replace command list view and command list debugging code with something more sophisticated.

Note: There is a pre-existing issue with booting a new game in that it keeps the old EmuThread.
The GL code now supports this but the Core still doesn't.

Connect the emu_thread start/finish to a moveContext slot.

These avoid relying on memset for clearing the arrays.

Changed HLE function return methods to be static inline functions.

Returning a copy of the string is what was likely meant to be done.

Most functions already operate on std::strings. This also removes the need to manually null terminate thread names.

entry_point would not be added to the string. Also used StringFromFormat
so that the buffer is unnecessary.

On POSIX systems mmap will return MAP_FAILED ((void*)-1) instead of a null pointer.

Also replaced C headers with the C++ equivalent ones

Fixes building with clang.

HID: Fix typo with DisableGyroscopeLow command.