sync: use ephemeral multiverse trees for sparse sync #2015

Job	Run time
Docker build check	2m 50s
Format check	28s
Compilation check	29s
cross compilation	8m 32s
run itests	2m 22s
run itests postgres	3m 12s
Lint check	2m 4s
go mod check	28s
RPC check	1m 10s
Sqlc check	21s
test vector check	56s
run unit tests (unit-race)	5m 0s
run unit tests (unit-cover)	2m 45s
run unit tests (unit dbbackend=postgres)	3m 48s
	34m 25s

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