Parallelizes `MDAnalysis.analysis.msd` #6748

Job	Run time
build_docs	4m 28s
sdist_check_and_build	8m 34s
main_tests (ubuntu-latest, 3.11, true, true)	24m 28s
main_tests (macos-13, 3.12, true, true, macOS_monterey_py311)	56m 32s
main_tests (ubuntu-latest, 3.10, true, true)	25m 6s
main_tests (ubuntu-latest, 3.13, false, true, python_313)	12m 48s
main_tests (ubuntu-latest, 3.10, true, false, asv_check, asv)	2m 48s
main_tests (ubuntu-latest, 3.10, false, true, numpy_min, numpy=1.23.2)	13m 37s
main_tests (ubuntu-latest, 3.12, true, true)	38m 24s
main_tests (macOS-14, 3.12, false, true, macOS_14_arm64_py312)	9m 3s
	3h 15m 48s

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