Add support for vertex-based mesh definitions in MJCF #164

Job	Run time
ubuntu-latest - Env all Release	7m 6s
ubuntu-latest - Env all Debug	7m 28s
ubuntu-latest - Env all-py39 Release	6m 54s
ubuntu-latest - Env all-py39 Debug	7m 34s
macos-latest - Env all Release	5m 24s
macos-latest - Env all Debug	3m 53s
macos-latest - Env all-py39 Release	6m 2s
macos-latest - Env all-py39 Debug	4m 36s
macos-13 - Env all Release	11m 37s
macos-13 - Env all Debug	7m 19s
macos-13 - Env all-py39 Release	9m 9s
macos-13 - Env all-py39 Debug	11m 54s
windows-latest - Env all Release	15m 10s
windows-latest - Env all-clang-cl Release	8m 4s
check-macos-linux-windows-pixi	2s
	1h 52m 12s

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