Fix: Selectable whether to key handling in IME

[rustbasic]

Fix: Selectable whether to key handling in IME

Fix Issues: Backspace & arrow keys are completely broken

• Related Fix: Backspace not working after IME input #4912
• Closes eframe Linux: Backspace & arrow keys are completely broken #5008
• Closes Fix: Selectable whether to support IME #5085
• Closes [regression] [eframe] Backspace and arrow keys don't work in TextEdit #5181

How about the default value is false on Linux and true on other platforms?
it's target_os lint error.

impl Default for TextEditStyle {
    fn default() -> Self {
        Self {
            #[cfg(target_os = "linux")]
            ime_key_handling: false,
            #[cfg(not(target_os = "linux"))]
            ime_key_handling: true,
        }
    }
}

[github-actions]

Preview available at https://egui-pr-preview.github.io/pr/5182-patch131
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