tapgarden: use lru.Cache for various new group caches #1460

Job	Run time
Docker build check	4m 19s
Format check	40s
Compilation check	39s
cross compilation	12m 55s
run itests	7m 30s
run itests postgres	12m 22s
Lint check	3m 24s
go mod check	35s
RPC check	1m 52s
Sqlc check	27s
test vector check	1m 22s
run unit tests (unit-race)	6m 20s
run unit tests (unit-cover)	5m 11s
run unit tests (unit dbbackend=postgres)	4m 24s
	1h 2m 0s

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