Add structural invariance and meanstructure identification options #928

Job	Run time
unit-tests / scheduled-run-check	1s
unit-tests / ubuntu-latest (R 4.3.1)	17m 49s
unit-tests / macOS-latest (R 4.3.1)	8m 5s
unit-tests / windows-latest (R 4.3.1)	12m 15s
	38m 10s

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