Make basic INLA interface and simple marginalisation routine #2160

Job	Run time
windows (windows-latest, 3.12, tests/statespace/filters/test_kalman_filter.py)	8m 23s
windows (windows-latest, 3.12, tests/model)	14m 22s
windows (windows-latest, 3.12, tests/statespace --ignore tests/statespace/core/test_statespace.py...	17m 25s
windows (windows-latest, 3.12, tests --ignore tests/model --ignore tests/statespace --ignore test...	19m 22s
windows (windows-latest, 3.12, tests/distributions)	13m 35s
windows (windows-latest, 3.12, tests/statespace/core/test_statespace.py)	14m 23s
ubuntu (ubuntu-latest, 3.11, tests/statespace/filters/test_kalman_filter.py)	3m 6s
ubuntu (ubuntu-latest, 3.11, tests/statespace/core/test_statespace.py)	10m 1s
ubuntu (ubuntu-latest, 3.11, tests/statespace --ignore tests/statespace/core/test_statespace.py -...	11m 32s
ubuntu (ubuntu-latest, 3.11, tests/model)	9m 42s
ubuntu (ubuntu-latest, 3.11, tests/distributions)	6m 52s
ubuntu (ubuntu-latest, 3.11, tests --ignore tests/model --ignore tests/statespace --ignore tests/...	11m 21s
all_tests	3s
	2h 20m 7s

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