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.

macaroons/security.go

@@ -1,6 +1,3 @@
-//go:build !rpctest
-// +build !rpctest
-
 package macaroons
 
 import "github.com/btcsuite/btcwallet/snacl"