Don't end history search on focus in/out events

Apparently VTE terminals send the "focus in" event whenever we re-enable
focus reporting. That's probably a sensible thing to do.

Anyway, our problem is simply that we accidentally end history search on these
focus events which are implemented as anonymous (unmappable) readline cmds.
Perhaps there should be a separate cmd category.

Focus events show up as key::Invalid which is a weird private use code point;
probably we can get rid of this key..

Fixes #10411

src/reader.rs

@@ -4631,6 +4631,8 @@ fn command_ends_history_search(c: ReadlineCmd) -> bool {
             | rl::EndOfHistory
             | rl::Repaint
             | rl::ForceRepaint
+            | rl::FocusIn
+            | rl::FocusOut
     )
 }