Desktop: Use multithreaded CEF event loop on Windows and Linux (#3076)

* Prototype multi threaded event loop

* Fix input event dispatch

* Remove dead code

* Reenable do_message_loop_work for macos targets

* Cleanup

* Review cleanup

* Remove outdated comment

* Attempt to fix texture import errors

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Co-authored-by: Timon Schelling <me@timon.zip>

desktop/src/cef.rs

@@ -20,6 +20,7 @@ use std::sync::mpsc::Receiver;
 use std::sync::{Arc, Mutex};
 use std::time::Instant;
 
+mod consts;
 mod context;
 mod dirs;
 mod input;
@@ -34,7 +35,7 @@ mod texture_import;
 #[cfg(feature = "accelerated_paint")]
 use texture_import::SharedTextureHandle;
 
-pub(crate) use context::{Context, InitError, Initialized, Setup, SetupError};
+pub(crate) use context::{CefContext, CefContextBuilder, InitError};
 use winit::event_loop::EventLoopProxy;
 
 pub(crate) trait CefEventHandler: Clone {