[custom channels]: generate unique script keys for HTLCs #3500

Job	Run time
Compilation check	4m 38s
cross compilation	16m 28s
Format check	3m 20s
Docker build check	3m 30s
run itests	12m 7s
run itests postgres	21m 4s
Lint check	6m 30s
migration version check	14s
go mod check	3m 13s
RPC check	4m 6s
run LiT tests	11m 32s
sample configuration check	4m 26s
Sqlc check	3m 16s
test vector check	4m 0s
run unit tests (unit-race)	11m 30s
run unit tests (unit-cover)	7m 4s
run unit tests (unit dbbackend=postgres)	5m 19s
finish	3s
	2h 2m 20s

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