This patch adds support for canceling compositor evaluations for the
realtime compositor. Only the canceling of the Denoise operation is
supported for now. That's because inter-operation canceling is not
feasible since all work will have been submitted to the GPU driver
before the user is able to cancel. So some kind of blocking operations
would need to used to actually allow canceling, which is not something
we are going to investigate as part of this patch.
Pull Request: https://projects.blender.org/blender/blender/pulls/117725
e7ffe74920