Desktop: Implement GPU accelerated offscreen rendering and improve rendering efficency (#3056)

* WIP accelerade offscreen canvas implementation

* Implement vulkan dmabuf import

* Add fps printing

* Add feature gates

* Forgot to add file

* Experimental windows support

* Cast ptr to isize

* Remove testing chrome://flags url

* Experimental macos support for texture import

* Cleanup code and improve latency / frame pacing

* Add path for importing textures on windows through dx12

* Update doc comment

* Import textures through metal on macos

* Review cleanup

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

desktop/src/consts.rs

@@ -1,3 +1,7 @@
 pub(crate) static APP_NAME: &str = "Graphite";
 pub(crate) static APP_ID: &str = "rs.graphite.GraphiteEditor";
 pub(crate) static APP_DIRECTORY_NAME: &str = "graphite-editor";
+
+// CEF configuration constants
+pub(crate) const CEF_WINDOWLESS_FRAME_RATE: i32 = 60;
+pub(crate) const CEF_MESSAGE_LOOP_MAX_ITERATIONS: usize = 10;