Editor crash when loading large images

[TrueDoctor]

When Trying to open a large image in the editor, it crashes after some while. This is likely caused by our animation loop not playing nice with such a long-running task on the main thread

[TrueDoctor]

After fixing the mutex errors, this seems to be related to the image serialization.

[TrueDoctor]

This might actually be a memory issue as the in memory representation takes 384mb which is quite substantial

[0HyperCube]

The crash shown is from the autosaving (see all the serde in the call stack). This will likely be solved as part of #1604.

[Keavon]

See also discussion in #1231 which is a duplicate of this.