hardware wallets: mention keystore.label in select_device

Without it, it is not clear for which keystore the user is supposed to select the device.
(though note that not all plugins implement labels, e.g. ledger does not)

related: https://github.com/spesmilo/electrum/issues/4199#issuecomment-1112552416

electrum/plugin.py

@@ -632,7 +632,7 @@ class DeviceMgr(ThreadJob):
             if not allow_user_interaction:
                 raise CannotAutoSelectDevice()
             msg = _('Please insert your {}').format(plugin.device)
-            if keystore.label:
+            if keystore.label and keystore.label not in PLACEHOLDER_HW_CLIENT_LABELS:
                 msg += ' ({})'.format(keystore.label)
             msg += '. {}\n\n{}'.format(
                 _('Verify the cable is connected and that '
@@ -671,7 +671,12 @@ class DeviceMgr(ThreadJob):
         if not allow_user_interaction:
             raise CannotAutoSelectDevice()
         # ask user to select device manually
-        msg = _("Please select which {} device to use:").format(plugin.device)
+        msg = ""
+        if keystore.label and keystore.label not in PLACEHOLDER_HW_CLIENT_LABELS:
+            msg += _(
+                """Could not automatically pair with device """
+                """for keystore labelled "{}".\n""").format(keystore.label)
+        msg += _("Please select which {} device to use:").format(plugin.device)
         descriptions = ["{label} ({maybe_model}{init}, {transport})"
                         .format(label=info.label or _("An unnamed {}").format(info.plugin_name),
                                 init=(_("initialized") if info.initialized else _("wiped")),