replace waypoint pointers with waypoint indexes #4657

Job	Run time
Windows (Debug, MSVC, Win32)	10m 24s
Mac (Debug, clang, x86_64)	13m 0s
Windows (Debug, MSVC, x64)	10m 11s
Linux (Debug, gcc-9)	11m 36s
Windows (Release, MSVC, Win32)	16m 30s
Linux (Debug, gcc-13)	9m 59s
Mac (Debug, clang, arm64)	5m 44s
Windows (Release, MSVC, x64)	17m 49s
Mac (Release, clang, x86_64)	11m 10s
Mac (Release, clang, arm64)	5m 17s
Linux (Debug, clang-16)	12m 44s
Linux (Release, gcc-9)	7m 13s
Linux (Release, gcc-13)	8m 48s
Linux (Release, clang-16)	10m 37s
Linux (Debug, gcc-13, -DFSO_BUILD_WITH_OPENGL=OFF -DFSO_BUILD_WITH_VULKAN=OFF)	9m 43s
Linux (Release, gcc-13, -DFSO_BUILD_WITH_OPENGL=OFF -DFSO_BUILD_WITH_VULKAN=OFF)	8m 41s
	2h 49m 26s

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