Refactor GroupKey unit tests. #3824

Job	Run time
cross compilation	12m 24s
Docker build check	3m 39s
Compilation check	1m 40s
Format check	24s
run itests	11m 56s
run itests postgres	20m 26s
Lint check	2m 42s
migration version check	13s
go mod check	21s
RPC check	1m 12s
run LiT tests	17m 13s
sample configuration check	40s
Sqlc check	2m 40s
test vector check	56s
run unit tests (unit-race)	15m 4s
run unit tests (unit-cover)	4m 42s
run unit tests (unit dbbackend=postgres)	6m 10s
finish	6s
	1h 42m 28s

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