Realisation improvements, dummy store support, unit testing #19953

Job	Run time
pre-commit checks	1m 21s
eval	54s
Check presence of secrets	2s
aggregate basic checks	4s
vm_tests	20m 33s
tests on macos	6m 51s
tests on ubuntu	11m 11s
tests on ubuntu (with sanitizers / coverage)	12m 47s
installer test ${{ matrix.scenario }}	0s
profile_build	0s
flake_regressions	2m 4s
docker_push_image	0s
	55m 47s

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