tapchannel: enforce strict forwarding for asset invoices #3300

Job	Run time
RPC check	1m 19s
Sqlc check	31s
test vector check	42s
go mod check	20s
cross compilation	12m 37s
Compilation check	33s
Docker build check	3m 46s
Format check	20s
run itests postgres	19m 23s
run itests	10m 57s
Lint check	2m 17s
migration version check	14s
run LiT tests	13m 16s
sample configuration check	27s
run unit tests (unit-race)	7m 22s
run unit tests (unit-cover)	1m 46s
run unit tests (unit dbbackend=postgres)	5m 32s
finish	6s
	1h 21m 28s

Provide feedback