Update and Refactor `find_MAP` and `fit_laplace` #1921

Job	Run time
windows (windows-latest, 3.12, tests/statespace/filters/test_kalman_filter.py)	4m 55s
windows (windows-latest, 3.12, tests/model)	13m 55s
windows (windows-latest, 3.12, tests/statespace --ignore tests/statespace/core/test_statespace.py...	11m 11s
ubuntu (ubuntu-latest, 3.11, tests/model)	8m 55s
windows (windows-latest, 3.12, tests/statespace/core/test_statespace.py)	9m 45s
windows (windows-latest, 3.12, tests/distributions)	10m 31s
windows (windows-latest, 3.12, tests --ignore tests/model --ignore tests/statespace --ignore test...	17m 44s
ubuntu (ubuntu-latest, 3.11, tests/statespace/core/test_statespace.py)	6m 19s
ubuntu (ubuntu-latest, 3.11, tests/distributions)	6m 16s
ubuntu (ubuntu-latest, 3.11, tests/statespace/filters/test_kalman_filter.py)	2m 30s
ubuntu (ubuntu-latest, 3.11, tests --ignore tests/model --ignore tests/statespace --ignore tests/...	9m 40s
ubuntu (ubuntu-latest, 3.11, tests/statespace --ignore tests/statespace/core/test_statespace.py -...	7m 42s
all_tests	2s
	1h 49m 25s

Provide feedback