[3/3]: Implement `Consumer` on `chainWatcher` and resolvers #448

Job	Run time
check commits	8m 1s
RPC and mobile compilation check	2m 11s
cross compilation	8m 1s
check pinned dependencies (google.golang.org/grpc v1.59.0)	4s
lint code	3m 52s
check pinned dependencies (github.com/golang/protobuf v1.5.3)	3s
sample configuration check	50s
Sqlc check	37s
run unit tests (btcd unit-cover)	5m 54s
run macOS itest	7m 19s
run unit tests (unit tags="kvdb_etcd")	5m 43s
run unit tests (unit tags="kvdb_postgres")	4m 1s
run unit tests (unit tags="kvdb_sqlite")	1m 33s
check release notes updated	6s
run ubuntu itests (btcd, backend=btcd cover=1)	1s
run unit tests (btcd unit-race)	7m 3s
run ubuntu itests (bitcoind, backend=bitcoind cover=1)	1s
run windows itest	7m 1s
run unit tests (unit-module)	1s
run ubuntu itests (bitcoind-notxindex, backend="bitcoind notxindex")	1s
run ubuntu itests (bitcoind-rpcpolling, backend="bitcoind rpcpolling" cover=1)	1s
run ubuntu itests (bitcoind-etcd, backend=bitcoind dbbackend=etcd)	1s
run ubuntu itests (bitcoind-postgres, backend=bitcoind dbbackend=postgres)	1s
run ubuntu itests (bitcoind-sqlite, backend=bitcoind dbbackend=sqlite)	1s
run ubuntu itests (bitcoind-postgres-nativesql, backend=bitcoind dbbackend=postgres nativesql=true)	1s
run ubuntu itests (bitcoind-sqlite-nativesql, backend=bitcoind dbbackend=sqlite nativesql=true)	1s
run ubuntu itests (neutrino, backend=neutrino cover=1)	1s
finish	3s
	1h 2m 33s

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