[i18n]Allow X11 File dialog button text customization

[rabbitism]

Is your feature request related to a problem? Please describe.

Avalonia/src/Avalonia.X11/NativeDialogs/GtkNativeFileDialogs.cs

Lines 186 to 189 in aa858f3

	using (var open = new Utf8Buffer(
	action == GtkFileChooserAction.Save ? "Save"
	: action == GtkFileChooserAction.SelectFolder ? "Select"
	: "Open"))

The button text is hardcoded in English, should be customizable.

Describe the solution you'd like

Should be part of X11PlatformOptions

Describe alternatives you've considered

No response

Additional context

No response