qml: fix invalid QEInvoiceParser state

Fixes the issue described in #10406.
When scanning a lightning invoice we would pass it to
`QEInvoiceParser.fromResolvedPaymentIdentifier()`, however
`fromResolvedPaymentIdentifier()` doesn't reset the state of
`QEInvoiceParser._lnurlData` which is used in QML to evaluate
`payImmediately: invoiceParser.isLnurlPay` in the `onValidationSuccess`
connection.

This change calls `clear()` in `fromResolvedPaymentIdentifier()` to
ensure that `QEInvoiceParser` state gets reset when loading a new invoice.
However when retrieving a bolt11 from a lnurl-pay callback we don't
wan't to reset `QEInvoiceParser._lnurlData` so that `payImmediately` is
true when confirming the lnurl pay dialog, for that I skip calling
`fromResolvedPaymentIdentifier()` and instead call `validateRecipient()`
directly so the `QEInvoiceParser` state doesn't get reset in this case.

electrum/gui/qml/qeinvoice.py

@@ -451,7 +451,7 @@ class QEInvoiceParser(QEInvoice):
 
     @pyqtSlot(object)
     def fromResolvedPaymentIdentifier(self, resolved_pi: PaymentIdentifier) -> None:
-        self.canPay = False
+        self.clear()
         self.amountOverride = QEAmount()
         if resolved_pi:
             assert not resolved_pi.need_resolve()
@@ -653,7 +653,8 @@ class QEInvoiceParser(QEInvoice):
         if orig_amount * 1000 != invoice.amount_msat:  # TODO msat precision can cause trouble here
             raise Exception('Unexpected amount in invoice, differs from lnurl-pay specified amount')
 
-        self.fromResolvedPaymentIdentifier(
+        self.amountOverride = QEAmount()
+        self.validateRecipient(
             PaymentIdentifier(self._wallet.wallet, invoice.lightning_invoice)
         )