tests: Use manual bumps instead of bumpfee for resendwallettransactions

Bumpfee will try to increase the entire package to the target feerate,
which causes repeated bumpfees to quickly shoot up in fees, causing
intermittent failures when the fee is too large. We don't care about
this property, just that the child is continuously replaced until we
observe it's position in mapWallet is before its parent. Instead of
using bumpfee, we can create raw transactions which have only pay the
additional incremental relay fee, thus avoiding this problem.

test/functional/wallet_resendwallettransactions.py

@@ -5,6 +5,8 @@
 """Test that the wallet resends transactions periodically."""
 import time
 
+from decimal import Decimal
+
 from test_framework.blocktools import (
     create_block,
     create_coinbase,
@@ -15,6 +17,7 @@
 from test_framework.util import (
     assert_equal,
     assert_raises_rpc_error,
+    get_fee,
 )
 
 class ResendWalletTransactionsTest(BitcoinTestFramework):
@@ -86,18 +89,28 @@ def run_test(self):
         # ordering of mapWallet is, if the child is not before the parent, we will create a new
         # child (via bumpfee) and remove the old child (via removeprunedfunds) until we get the
         # ordering of child before parent.
-        child_txid = node.send(outputs=[{addr: 0.5}], inputs=[{"txid":txid, "vout":0}])["txid"]
+        child_inputs = [{"txid": txid, "vout": 0}]
+        child_txid = node.sendall(recipients=[addr], inputs=child_inputs)["txid"]
+        # Get the child tx's info for manual bumping
+        child_tx_info = node.gettransaction(txid=child_txid, verbose=True)
+        child_output_value = child_tx_info["decoded"]["vout"][0]["value"]
+        additional_child_fee = get_fee(child_tx_info["decoded"]["vsize"], Decimal(0.00001100))
         while True:
             txids = node.listreceivedbyaddress(minconf=0, address_filter=addr)[0]["txids"]
             if txids == [child_txid, txid]:
                 break
-            bumped = node.bumpfee(child_txid)
+            # Manually bump the tx
+            # The inputs and the output address stay the same, just changing the amount for the new fee
+            child_output_value -= additional_child_fee
+            bumped_raw = node.createrawtransaction(inputs=child_inputs, outputs=[{addr: child_output_value}])
+            bumped = node.signrawtransactionwithwallet(bumped_raw)
+            bumped_txid = node.sendrawtransaction(bumped["hex"])
             # The scheduler queue creates a copy of the added tx after
             # send/bumpfee and re-adds it to the wallet (undoing the next
             # removeprunedfunds). So empty the scheduler queue:
             node.syncwithvalidationinterfacequeue()
             node.removeprunedfunds(child_txid)
-            child_txid = bumped["txid"]
+            child_txid = bumped_txid
         entry_time = node.getmempoolentry(child_txid)["time"]
 
         block_time = entry_time + 6 * 60