[custom channels]: generate unique script keys for HTLCs #3471

Job	Run time
cross compilation	4m 38s
Compilation check	49s
Format check	21s
Docker build check	3m 43s
run itests	8m 53s
Lint check	2m 40s
run itests postgres	17m 26s
migration version check	12s
go mod check	29s
RPC check	1m 12s
run LiT tests	16m 29s
sample configuration check	44s
Sqlc check	2m 41s
test vector check	49s
run unit tests (unit-race)	9m 24s
run unit tests (unit-cover)	2m 52s
run unit tests (unit dbbackend=postgres)	5m 51s
finish	5s
	1h 19m 18s

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