Desktop: Isolate CEF-rendered UI into separate crate and process (#4321)

* Extract CEF rendered UI into a separate process and crate

* Review

* Review

* Review

* Review

* Remove necessary workarounds

* Block on frame copy ack

* Crop and resample frames correctly

* Skip blank frames

* Fix deps

* Fix fmt

* Fix clippy warning

* Review

* Fix todo

desktop/platform/linux/src/main.rs

@@ -1,3 +1,3 @@
-fn main() {
-	graphite_desktop::start();
+fn main() -> std::process::ExitCode {
+	graphite_desktop::start()
 }