linux: Fix some panics related to xkb compose (#13529)

Release Notes:

- N/A

Fixed #13463 Fixed crash when the locale was non UTF-8 and fixed the
fallback locale.
Fixed #13010 Fixed crash when `compose.keysym()` was `XKB_KEY_NoSymbol`

I also extracted the `xkb_compose_state` to a single place

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

@@ -3,6 +3,7 @@
 use std::any::{type_name, Any};
 use std::cell::{self, RefCell};
 use std::env;
+use std::ffi::OsString;
 use std::fs::File;
 use std::io::Read;
 use std::ops::{Deref, DerefMut};
@@ -508,6 +509,27 @@ pub(super) fn is_within_click_distance(a: Point<Pixels>, b: Point<Pixels>) -> bo
     diff.x.abs() <= DOUBLE_CLICK_DISTANCE && diff.y.abs() <= DOUBLE_CLICK_DISTANCE
 }
 
+pub(super) fn get_xkb_compose_state(cx: &xkb::Context) -> Option<xkb::compose::State> {
+    let mut locales = Vec::default();
+    if let Some(locale) = std::env::var_os("LC_CTYPE") {
+        locales.push(locale);
+    }
+    locales.push(OsString::from("C"));
+    let mut state: Option<xkb::compose::State> = None;
+    for locale in locales {
+        if let Ok(table) =
+            xkb::compose::Table::new_from_locale(&cx, &locale, xkb::compose::COMPILE_NO_FLAGS)
+        {
+            state = Some(xkb::compose::State::new(
+                &table,
+                xkb::compose::STATE_NO_FLAGS,
+            ));
+            break;
+        }
+    }
+    state
+}
+
 pub(super) unsafe fn read_fd(mut fd: FileDescriptor) -> Result<String> {
     let mut file = File::from_raw_fd(fd.as_raw_fd());