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* Remove outdated comment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/consts.rs

@@ -0,0 +1,2 @@
+pub(crate) const GRAPHITE_SCHEME: &str = "graphite-static";
+pub(crate) const FRONTEND_DOMAIN: &str = "frontend";