Use faster nix installer action and cache for CI #5070

Job	Run time
Test (shuffled order)	3m 44s
Build wheel	2m 54s
Test Typescript	2m 39s
Test + Coverage	4m 13s
Linter	3m 9s
Test if testdata is up to date	3m 16s
Formatting	2m 36s
Test Frontend	5m 12s
Build nix environment on MacOS	7m 54s
MyPy	2m 38s
Install wheel with system Python	19s
Backup process	1m 51s
	40m 25s

Provide feedback