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.

sweep/defaults.go

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

sweep/defaults_rpctest.go

@@ -1,18 +0,0 @@
-//go:build rpctest
-// +build rpctest
-
-package sweep
-
-import (
-	"time"
-)
-
-var (
-	// DefaultBatchWindowDuration specifies duration of the sweep batch
-	// window. The sweep is held back during the batch window to allow more
-	// inputs to be added and thereby lower the fee per input.
-	//
-	// To speed up integration tests waiting for a sweep to happen, the
-	// batch window is shortened.
-	DefaultBatchWindowDuration = 8 * time.Second
-)