multi: add new config option BudgetConfig and NoDeadlineConfTarget

This commit adds a new group config `BudgetConfig` to allow users
specifying their own preference when sweeping outputs. And a new config
option `NoDeadlineConfTarget` is added in case the user wants to use a
different "lazy" conf target.

sweep/sweeper_test.go

@@ -2677,6 +2677,7 @@ func TestSweepPendingInputs(t *testing.T) {
 		GenSweepScript: func() ([]byte, error) {
 			return testPubKey.SerializeCompressed(), nil
 		},
+		NoDeadlineConfTarget: uint32(DefaultDeadlineDelta),
 	})
 
 	// Set a current height to test the deadline override.