Make basic INLA interface and simple marginalisation routine #2080

Job	Run time
ubuntu (ubuntu-latest, 3.11, tests/statespace/core/test_statespace.py)	59s
ubuntu (ubuntu-latest, 3.11, tests/model)	1m 5s
ubuntu (ubuntu-latest, 3.11, tests/statespace --ignore tests/statespace/core/test_statespace.py -...	1m 9s
ubuntu (ubuntu-latest, 3.11, tests/distributions)	58s
ubuntu (ubuntu-latest, 3.11, tests/statespace/filters/test_kalman_filter.py)	1m 44s
windows (windows-latest, 3.12, tests/model)	1m 32s
ubuntu (ubuntu-latest, 3.11, tests --ignore tests/model --ignore tests/statespace --ignore tests/...	1m 10s
windows (windows-latest, 3.12, tests/statespace --ignore tests/statespace/core/test_statespace.py...	1m 31s
windows (windows-latest, 3.12, tests/distributions)	1m 35s
windows (windows-latest, 3.12, tests/statespace/filters/test_kalman_filter.py)	1m 32s
windows (windows-latest, 3.12, tests/statespace/core/test_statespace.py)	1m 32s
windows (windows-latest, 3.12, tests --ignore tests/model --ignore tests/statespace --ignore test...	1m 30s
all_tests	2s
	16m 19s

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