Add structural invariance and meanstructure identification options #929

Job	Run time
unit-tests / scheduled-run-check	3s
unit-tests / ubuntu-latest (R 4.3.1)	14m 1s
unit-tests / macOS-latest (R 4.3.1)	13m 29s
unit-tests / windows-latest (R 4.3.1)	10m 21s
	37m 54s

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