Refactor CMake build system

[madebr]

• [x] Use CMakePresets.json for CI, this requires CMake 3.23 (=newest CMake release as the file uses new features)
• [x] Add conan recipe (/conanfile.py) to build dethrace with external libraries, available as a courtesy + useful for testing next bullet point
• [x] Move all vendored libraries to thirdparty/XXX/source. The CMakeLists.txt at thirdparty/XXX/CMakeLists.txt allows to switch between a system library and the vendored one. This can be tested by using the conanfile in the root.
• [x] All external libraries are updated to latest releases + custom modification are reverted
• [x] Optionally enable -Werror for select libraries (using the DETHRACE_WERROR configure option)
• [x] Build harness with -Wall + -Werror on CI (including MSVC)
• [x] Build BRender with -Wall + -Werror on CI (including MSVC)
• [x] Build BRender + DethRace in C90 mode
• [ ] Move dependency download script to a more central location + document (see next bullet point)
• [ ] Improve documentation

Fixes #117