gui: cpfp: calc parent fee for cpfp using wallet.get_tx_info

I am only making this change as it makes it simpler to do manual testing of CPFP-ing *local* txs.
That is, by changing a few easy-to-find lines of code, I can make the GUI allow CPFP-ing a local tx, but
without this change it errors out with "unknown fee for parent transaction".

If one has an incoming local tx saved in the wallet, adb.get_tx_fee(txid) returns None
(if the tx gets into the mempool, it will use the server-reported value instead).
In contrast, wallet.get_tx_info(tx).fee calls both wallet.get_wallet_delta(tx) and adb.get_tx_fee(txid),
making it more expensive but more complete.

electrum/address_synchronizer.py

@@ -757,6 +757,7 @@ class AddressSynchronizer(Logger, EventListener):
               incorrectly early-exit and return None, e.g. for not-all-ismine-input txs,
               where we could calculate the fee if we deserialized (but to see if we have all
               the parent txs available, we would have to deserialize first).
+              More expensive but more complete alternative: wallet.get_tx_info(tx).fee
         """
         # check if stored fee is available
         fee = self.db.get_tx_fee(txid, trust_server=False)

electrum/gui/qml/qetxfinalizer.py

@@ -755,7 +755,7 @@ class QETxCpfpFeeBumper(TxFeeSlider, TxMonMixin):
             return
 
         self._parent_tx_size = self._parent_tx.estimated_size()
-        self._parent_fee = self._wallet.wallet.adb.get_tx_fee(self._txid)
+        self._parent_fee = self._wallet.wallet.get_tx_info(self._parent_tx).fee
 
         if self._parent_fee is None:
             self._logger.error(_("Can't CPFP: unknown fee for parent transaction."))

electrum/gui/qt/main_window.py

@@ -2546,7 +2546,7 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger, QtEventListener):
         total_size = parent_tx.estimated_size() + new_tx.estimated_size()
         parent_txid = parent_tx.txid()
         assert parent_txid
-        parent_fee = self.wallet.adb.get_tx_fee(parent_txid)
+        parent_fee = self.wallet.get_tx_info(parent_tx).fee
         if parent_fee is None:
             self.show_error(_("Can't CPFP: unknown fee for parent transaction."))
             return