channeldb+lnwire: rename MsgFundingLocked to MsgChannelReady

This commit is created by running,

```shell
gofmt -d -w -r 'MsgFundingLocked -> MsgChannelReady' .

gco master channeldb/migration
```

lnwire/lnwire_test.go

@@ -566,7 +566,7 @@ func TestLightningWireProtocol(t *testing.T) {
 
 			v[0] = reflect.ValueOf(req)
 		},
-		MsgFundingLocked: func(v []reflect.Value, r *rand.Rand) {
+		MsgChannelReady: func(v []reflect.Value, r *rand.Rand) {
 
 			var c [32]byte
 			if _, err := r.Read(c[:]); err != nil {
@@ -1013,7 +1013,7 @@ func TestLightningWireProtocol(t *testing.T) {
 			},
 		},
 		{
-			msgType: MsgFundingLocked,
+			msgType: MsgChannelReady,
 			scenario: func(m ChannelReady) bool {
 				return mainScenario(&m)
 			},