sweep: make sweeper aware of unconfirmed parent transactions.

Extend the fee estimator to take into account parent transactions with
their weights and fees.

Do not try to cpfp parent transactions that have a higher fee rate than
the sweep tx fee rate.

sweep/test_utils.go

@@ -13,6 +13,7 @@ import (
 
 var (
 	defaultTestTimeout = 5 * time.Second
+	processingDelay    = 1 * time.Second
 	mockChainHash, _   = chainhash.NewHashFromStr("00aabbccddeeff")
 	mockChainHeight    = int32(100)
 )