Update and Refactor `find_MAP` and `fit_laplace` #1917

Job	Run time
ubuntu (ubuntu-latest, 3.11, tests/statespace/core/test_statespace.py)	6m 20s
ubuntu (ubuntu-latest, 3.11, tests/model)	6m 55s
ubuntu (ubuntu-latest, 3.11, tests/statespace/filters/test_kalman_filter.py)	2m 31s
windows (windows-latest, 3.12, tests/statespace --ignore tests/statespace/core/test_statespace.py...	6m 47s
ubuntu (ubuntu-latest, 3.11, tests/distributions)	6m 12s
windows (windows-latest, 3.12, tests/statespace/core/test_statespace.py)	6m 46s
ubuntu (ubuntu-latest, 3.11, tests/statespace --ignore tests/statespace/core/test_statespace.py -...	6m 56s
ubuntu (ubuntu-latest, 3.11, tests --ignore tests/model --ignore tests/statespace --ignore tests/...	6m 56s
windows (windows-latest, 3.12, tests/statespace/filters/test_kalman_filter.py)	5m 51s
windows (windows-latest, 3.12, tests/model)	6m 45s
windows (windows-latest, 3.12, tests --ignore tests/model --ignore tests/statespace --ignore test...	6m 50s
windows (windows-latest, 3.12, tests/distributions)	6m 50s
all_tests	2s
	1h 15m 41s

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