Replace `stdafx.h` with `pch/main-pch.hpp`

[alef]

Summary

Build "Use one precompiled header"

Purpose of change

Since stdafx.h and pch/main-pch.hpp are quite similar, let us use only one.

Describe the solution

• [x] Merged stdafx.h content into pch/main-pch.hpp
• [x] Changed the msvc-full-features solution files to point to the new include
• [x] stdafx.cpp includes the new pch

Describe alternatives you've considered

Testing

Compile and link the following:

• [x] Visual Studio msvc-full-features Solution
• [x] Linux Makefile with TILES=1 SOUND=1 CCACHE=1 PCH=1
• [x] CMake MSYS2/MINGW/UCRT64
• [x] CMake MSVC

Additional context

Keep this in draft for some time to double check local builds performance.

[akrieger]

Are all the project file changes needed, or are those some intermediate steps? Everything should be expressable in Cataclysm-common.props.