rpc: implement DecodeAssetInvoice #3604

Job	Run time
Compilation check	37s
Docker build check	3m 46s
cross compilation	3m 54s
Format check	22s
run itests	11m 1s
run itests postgres	18m 44s
Lint check	3m 42s
migration version check	15s
go mod check	24s
RPC check	1m 11s
run LiT tests	13m 30s
sample configuration check	30s
Sqlc check	30s
test vector check	42s
run unit tests (unit-race)	11m 13s
run unit tests (unit-cover)	2m 21s
run unit tests (unit dbbackend=postgres)	5m 57s
finish	4s
	1h 18m 43s

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