channeldb+kvdb: an extended STM on top of etcd clientv3

This commit adds an extended STM, similar to what available in etcd's
clientv3 module. This incarnation of said STM supports additional
features, like positioning in key intervals while taking into account
deletes and writes as well. This is a preliminary work to support all
features of the kvdb interface.

go.mod

@@ -14,10 +14,18 @@ require (
 	github.com/btcsuite/btcwallet/wallet/txrules v1.0.0
 	github.com/btcsuite/btcwallet/walletdb v1.3.1
 	github.com/btcsuite/btcwallet/wtxmgr v1.1.1-0.20200515224913-e0e62245ecbe
+	github.com/coreos/etcd v3.3.18+incompatible
+	github.com/coreos/go-semver v0.3.0 // indirect
+	github.com/coreos/go-systemd v0.0.0-00010101000000-000000000000 // indirect
+	github.com/coreos/pkg v0.0.0-20180928190104-399ea9e2e55f // indirect
 	github.com/davecgh/go-spew v1.1.1
+	github.com/dgrijalva/jwt-go v3.2.0+incompatible // indirect
 	github.com/go-errors/errors v1.0.1
 	github.com/go-openapi/strfmt v0.19.5 // indirect
+	github.com/golang/groupcache v0.0.0-20200121045136-8c9f03a8e57e // indirect
 	github.com/golang/protobuf v1.3.1
+	github.com/google/btree v1.0.0 // indirect
+	github.com/gorilla/websocket v1.4.1 // indirect
 	github.com/grpc-ecosystem/go-grpc-middleware v1.0.0
 	github.com/grpc-ecosystem/go-grpc-prometheus v1.2.0
 	github.com/grpc-ecosystem/grpc-gateway v1.8.6
@@ -25,7 +33,9 @@ require (
 	github.com/jackpal/go-nat-pmp v0.0.0-20170405195558-28a68d0c24ad
 	github.com/jedib0t/go-pretty v4.3.0+incompatible
 	github.com/jessevdk/go-flags v1.4.0
+	github.com/jonboulle/clockwork v0.1.0 // indirect
 	github.com/jrick/logrotate v1.0.0
+	github.com/json-iterator/go v1.1.9 // indirect
 	github.com/juju/clock v0.0.0-20190205081909-9c5c9712527c // indirect
 	github.com/juju/errors v0.0.0-20190806202954-0232dcc7464d // indirect
 	github.com/juju/loggo v0.0.0-20190526231331-6e530bcce5d8 // indirect
@@ -43,12 +53,19 @@ require (
 	github.com/ltcsuite/ltcd v0.0.0-20190101042124-f37f8bf35796
 	github.com/mattn/go-runewidth v0.0.9 // indirect
 	github.com/miekg/dns v0.0.0-20171125082028-79bfde677fa8
+	github.com/modern-go/reflect2 v1.0.1 // indirect
 	github.com/prometheus/client_golang v0.9.3
 	github.com/rogpeppe/fastuuid v1.2.0 // indirect
+	github.com/soheilhy/cmux v0.1.4 // indirect
+	github.com/stretchr/testify v1.4.0
+	github.com/tmc/grpc-websocket-proxy v0.0.0-20190109142713-0ad062ec5ee5 // indirect
 	github.com/tv42/zbase32 v0.0.0-20160707012821-501572607d02
 	github.com/urfave/cli v1.18.0
+	github.com/xiang90/probing v0.0.0-20190116061207-43a291ad63a2 // indirect
+	go.etcd.io/bbolt v1.3.3
+	go.uber.org/zap v1.14.1 // indirect
 	golang.org/x/crypto v0.0.0-20200510223506-06a226fb4e37
-	golang.org/x/net v0.0.0-20190206173232-65e2d4e15006
+	golang.org/x/net v0.0.0-20190620200207-3b0461eec859
 	golang.org/x/sys v0.0.0-20200116001909-b77594299b42 // indirect
 	golang.org/x/time v0.0.0-20180412165947-fbb02b2291d2
 	google.golang.org/genproto v0.0.0-20190201180003-4b09977fb922
@@ -57,6 +74,7 @@ require (
 	gopkg.in/macaroon-bakery.v2 v2.0.1
 	gopkg.in/macaroon.v2 v2.0.0
 	gopkg.in/mgo.v2 v2.0.0-20190816093944-a6b53ec6cb22 // indirect
+	sigs.k8s.io/yaml v1.1.0 // indirect
 )
 
 replace github.com/lightningnetwork/lnd/ticker => ./ticker
@@ -71,4 +89,6 @@ replace git.schwanenlied.me/yawning/bsaes.git => github.com/Yawning/bsaes v0.0.0
 // btcsuite/btcutil package requests a newer version.
 replace golang.org/x/crypto => golang.org/x/crypto v0.0.0-20190211182817-74369b46fc67
 
+replace github.com/coreos/go-systemd => github.com/coreos/go-systemd/v22 v22.0.0
+
 go 1.12