qt: fix: bip70 pay reqs need x509 verification

regression from https://github.com/spesmilo/electrum/pull/8462

- pr.verify() was called in qml, but not in qt gui
- we now call pr.verify() in get_payment_request(), to make the API less error-prone
- it is now ok to call pr.verify() multiple times, the result is cached

electrum/gui/kivy/main_window.py

@@ -459,7 +459,7 @@ class ElectrumWindow(App, Logger, EventListener):
         if not self.wallet:
             self.show_error(_('No wallet loaded.'))
             return
-        if pr.verify(self.wallet.contacts):
+        if pr.verify():
             invoice = Invoice.from_bip70_payreq(pr, height=0)
             if invoice and self.wallet.get_invoice_status(invoice) == PR_PAID:
                 self.show_error("invoice already paid")

electrum/gui/qml/qeinvoice.py

@@ -473,7 +473,7 @@ class QEInvoiceParser(QEInvoice):
 
     def _bip70_payment_request_resolved(self, pr: 'PaymentRequest'):
         self._logger.debug('resolved payment request')
-        if pr.verify(self._wallet.wallet.contacts):
+        if pr.verify():
             invoice = Invoice.from_bip70_payreq(pr, height=0)
             if self._wallet.wallet.get_invoice_status(invoice) == PR_PAID:
                 self.validationError.emit('unknown', _('Invoice already paid'))

electrum/gui/qt/main_window.py

@@ -1438,7 +1438,7 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger, QtEventListener):
             grid.addWidget(QLabel(format_time(invoice.exp + invoice.time)), 4, 1)
         if invoice.bip70:
             pr = paymentrequest.PaymentRequest(bytes.fromhex(invoice.bip70))
-            pr.verify(self.contacts)
+            pr.verify()
             grid.addWidget(QLabel(_("Requestor") + ':'), 5, 0)
             grid.addWidget(QLabel(pr.get_requestor()), 5, 1)
             grid.addWidget(QLabel(_("Signature") + ':'), 6, 0)