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"

macaroons/security_integration.go

@@ -1,15 +1,14 @@
-//go:build rpctest
-// +build rpctest
+//go:build integration
 
 package macaroons
 
 import "github.com/btcsuite/btcwallet/waddrmgr"
 
-var (
+func init() {
 	// Below are the reduced scrypt parameters that are used when creating
 	// the encryption key for the macaroon database with snacl.NewSecretKey.
 	// We use very low values for our itest/rpctest to speed things up.
 	scryptN = waddrmgr.FastScryptOptions.N
 	scryptR = waddrmgr.FastScryptOptions.R
 	scryptP = waddrmgr.FastScryptOptions.P
-)
+}