x11: Add XIM support (#11657)

This pull request adds XIM (X Input Method) support to x11 platform.

The implementation utilizes [xim-rs](https://crates.io/crates/xim), a
XIM library written entirely in Rust, to provide asynchronous XIM
communication.
Preedit and candidate positioning are fully supported in the editor
interface, yet notably absent in the terminal environment.

This work is sponsored by [Rainlab Inc.](https://rainlab.co.jp/en/)

Release Notes:
- N/A

---------

Signed-off-by: npmania <np@mkv.li>

crates/gpui/src/platform/linux/x11/window.rs

@@ -478,6 +478,40 @@ impl X11WindowStatePtr {
         }
     }
 
+    pub fn handle_ime_commit(&self, text: String) {
+        let mut state = self.state.borrow_mut();
+        if let Some(mut input_handler) = state.input_handler.take() {
+            drop(state);
+            input_handler.replace_text_in_range(None, &text);
+            let mut state = self.state.borrow_mut();
+            state.input_handler = Some(input_handler);
+        }
+    }
+
+    pub fn handle_ime_preedit(&self, text: String) {
+        let mut state = self.state.borrow_mut();
+        if let Some(mut input_handler) = state.input_handler.take() {
+            drop(state);
+            input_handler.replace_and_mark_text_in_range(None, &text, None);
+            let mut state = self.state.borrow_mut();
+            state.input_handler = Some(input_handler);
+        }
+    }
+
+    pub fn get_ime_area(&self) -> Option<Bounds<Pixels>> {
+        let mut state = self.state.borrow_mut();
+        let mut bounds: Option<Bounds<Pixels>> = None;
+        if let Some(mut input_handler) = state.input_handler.take() {
+            drop(state);
+            if let Some(range) = input_handler.selected_text_range() {
+                bounds = input_handler.bounds_for_range(range);
+            }
+            let mut state = self.state.borrow_mut();
+            state.input_handler = Some(input_handler);
+        };
+        bounds
+    }
+
     pub fn configure(&self, bounds: Bounds<i32>) {
         let mut resize_args = None;
         let do_move;