Make basic INLA interface and simple marginalisation routine #1930

Job	Run time
windows (windows-latest, 3.12, tests/statespace/filters/test_kalman_filter.py)	4m 46s
windows (windows-latest, 3.12, tests/statespace/core/test_statespace.py)	9m 37s
windows (windows-latest, 3.12, tests/model)	13m 16s
windows (windows-latest, 3.12, tests/statespace --ignore tests/statespace/core/test_statespace.py...	11m 36s
windows (windows-latest, 3.12, tests/distributions)	11m 10s
windows (windows-latest, 3.12, tests --ignore tests/model --ignore tests/statespace --ignore test...	23m 13s
ubuntu (ubuntu-latest, 3.11, tests/statespace/filters/test_kalman_filter.py)	2m 33s
ubuntu (ubuntu-latest, 3.11, tests/statespace/core/test_statespace.py)	6m 10s
ubuntu (ubuntu-latest, 3.11, tests/statespace --ignore tests/statespace/core/test_statespace.py -...	7m 32s
ubuntu (ubuntu-latest, 3.11, tests --ignore tests/model --ignore tests/statespace --ignore tests/...	14m 11s
ubuntu (ubuntu-latest, 3.11, tests/distributions)	6m 10s
ubuntu (ubuntu-latest, 3.11, tests/model)	8m 53s
all_tests	2s
	1h 59m 9s

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