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.

lnwallet/btcwallet/btcwallet_integration.go

@@ -1,5 +1,4 @@
-//go:build rpctest || lowscrypt
-// +build rpctest lowscrypt
+//go:build integration || lowscrypt
 
 package btcwallet
 

lnwallet/revocation_producer.go

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

lnwallet/revocation_producer_itest.go

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