linux: Fix IME panel position while enumerating input methods (#12495)

Release Notes:

- N/A

This updates the IME position every time the selection changes, this is
probably only useful when you enumerate languages with your IME.

TODO:
- ~There is a rare chance that the ime panel is not updated because the
window input handler is None.~
- ~Update IME panel in vim mode.~
- ~Update IME panel when leaving Buffer search input.~

---------

Co-authored-by: Mikayla Maki <mikayla@zed.dev>

crates/gpui/src/platform/test/window.rs

@@ -279,6 +279,8 @@ impl PlatformWindow for TestWindow {
         unimplemented!()
     }
 
+    fn update_ime_position(&self, _bounds: Bounds<Pixels>) {}
+
     fn gpu_specs(&self) -> Option<GPUSpecs> {
         None
     }