multi: add new build tag integration

This commit adds a new build tag `integration` and removes the old tag
`rpctest` for clarity. Multiple unnecessary usages of `build !rpctest`
is also removed.

lncfg/address_test.go

@@ -1,6 +1,3 @@
-//go:build !rpctest
-// +build !rpctest
-
 package lncfg
 
 import (

lncfg/protocol.go

@@ -1,5 +1,4 @@
-//go:build !rpctest
-// +build !rpctest
+//go:build !integration
 
 package lncfg
 

lncfg/protocol_integration.go

@@ -1,5 +1,4 @@
-//go:build rpctest
-// +build rpctest
+//go:build integration
 
 package lncfg
 
@@ -7,6 +6,8 @@ package lncfg
 // compatibility of protocol additions, while defaulting to the latest within
 // lnd, or to enable experimental protocol changes.
 //
+// TODO(yy): delete this build flag to unify with `lncfg/protocol.go`.
+//
 //nolint:lll
 type ProtocolOptions struct {
 	// LegacyProtocol is a sub-config that houses all the legacy protocol