Simplify coin selection for sendcoins #14630

Job	Run time
lint code	4m 37s
check commits	6m 31s
cross compilation	25m 11s
check pinned dependencies (google.golang.org/grpc v1.59.0)	4s
run macOS itest	42m 1s
check pinned dependencies (github.com/golang/protobuf v1.5.3)	5s
check release notes updated	5s
RPC and mobile compilation check	2m 33s
sample configuration check	35s
Sqlc check	47s
run ubuntu itests (btcd, backend=btcd cover=1)	25m 25s
run unit tests (btcd unit-cover)	16m 54s
run ubuntu itests (bitcoind, backend=bitcoind cover=1)	32m 8s
run windows itest	43m 49s
run unit tests (unit tags="kvdb_etcd")	18m 24s
run ubuntu itests (bitcoind-notxindex, backend="bitcoind notxindex")	31m 19s
run unit tests (unit tags="kvdb_postgres")	17m 24s
run ubuntu itests (bitcoind-rpcpolling, backend="bitcoind rpcpolling" cover=1)	32m 51s
run unit tests (unit tags="kvdb_sqlite")	16m 27s
run ubuntu itests (bitcoind-etcd, backend=bitcoind dbbackend=etcd)	41m 43s
run unit tests (btcd unit-race)	35m 7s
run ubuntu itests (bitcoind-postgres, backend=bitcoind dbbackend=postgres)	1h 2m 38s
run unit tests (unit-module)	1m 33s
run ubuntu itests (bitcoind-sqlite, backend=bitcoind dbbackend=sqlite)	33m 49s
run ubuntu itests (bitcoind-postgres-nativesql, backend=bitcoind dbbackend=postgres nativesql=true)	58m 51s
run ubuntu itests (bitcoind-sqlite-nativesql, backend=bitcoind dbbackend=sqlite nativesql=true)	32m 56s
run ubuntu itests (neutrino, backend=neutrino cover=1)	31m 35s
finish	6s
	10h 15m 28s

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