Add dialpad to transfer dialog + various dialpad UI improvements (#6363)

Co-authored-by: Germain <germain@souquet.com>
Co-authored-by: Andrew Morgan <andrew@amorgan.xyz>
Co-authored-by: David Baker <dbkr@users.noreply.github.com>

src/components/views/context_menus/CallContextMenu.tsx

@@ -53,7 +53,7 @@ export default class CallContextMenu extends React.Component<IProps> {
     onTransferClick = () => {
         Modal.createTrackedDialog(
             'Transfer Call', '', InviteDialog, { kind: KIND_CALL_TRANSFER, call: this.props.call },
-            /*className=*/null, /*isPriority=*/false, /*isStatic=*/true,
+            /*className=*/"mx_InviteDialog_transferWrapper", /*isPriority=*/false, /*isStatic=*/true,
         );
         this.props.onFinished();
     };