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/ui/src/consts.rs

@@ -0,0 +1,37 @@
+use std::time::Duration;
+
+pub(crate) const RESOURCE_SCHEME: &str = "resources";
+pub(crate) const RESOURCE_DOMAIN: &str = "resources";
+
+pub(crate) const BROWSER_HOST_CONFIG_FLAG: &str = "--graphite-browser-host=";
+
+pub(crate) const WINDOWLESS_FRAME_RATE: i32 = 60;
+pub(crate) const FRAMES_IN_FLIGHT_LIMIT: u64 = 3;
+pub(crate) const FRAME_SEGMENT_POOL_SIZE: u64 = FRAMES_IN_FLIGHT_LIMIT + 1; // allow one extra staged frame
+pub(crate) const FRAME_SEGMENT_GRANULARITY: usize = 2 * 1024 * 1024; // 2 MiB
+#[cfg(feature = "accelerated_paint")]
+pub(crate) const FRAME_ACK_TIMEOUT: Duration = Duration::from_millis(250);
+
+pub(crate) const HOST_HELLO_TIMEOUT: Duration = Duration::from_secs(5);
+pub(crate) const HOST_SHUTDOWN_TIMEOUT: Duration = Duration::from_secs(5);
+
+#[cfg(target_os = "macos")]
+pub(crate) const IPC_BOOTSTRAP_PREFIX: &str = "art.graphite.Graphite.ipc.";
+
+pub(crate) const SCROLL_LINE_HEIGHT: usize = 40;
+pub(crate) const SCROLL_LINE_WIDTH: usize = 40;
+
+#[cfg(target_os = "linux")]
+pub(crate) const SCROLL_SPEED_X: f32 = 3.;
+#[cfg(target_os = "linux")]
+pub(crate) const SCROLL_SPEED_Y: f32 = 3.;
+
+#[cfg(not(target_os = "linux"))]
+pub(crate) const SCROLL_SPEED_X: f32 = 1.;
+#[cfg(not(target_os = "linux"))]
+pub(crate) const SCROLL_SPEED_Y: f32 = 1.;
+
+pub(crate) const PINCH_ZOOM_SPEED: f64 = 300.;
+
+pub(crate) const MULTICLICK_TIMEOUT: Duration = Duration::from_millis(500);
+pub(crate) const MULTICLICK_ALLOWED_TRAVEL: usize = 4;