Cleanup: Cycles X viewport drawing functions

Call them explicitly view_draw() while it is expected the code
operates within a 3d viewport context.

No functional changes. Is an internal Cycles change, which has
no affect on other engines.

Differential Revision: https://developer.blender.org/D12038

Cleanup: Remove commented out code in Cycles X GPU display

Merge branch 'master' into cycles-x

Fix missing passes update on Use Denoising change

Makes it so Render Layers node in the compositor is updated as soon
as Use Denoising is changed for the final render.

Differential Revision: https://developer.blender.org/D12010

Fix synchronization time included into constant time render in Cycles X

The first work is scheduled prior to scene update, and the scene update
might take a while first time (loading kernels, building all the internal
structures and so on).

Made it so the path tracer reports explicitly when it actually starts to
work, so that the scheduler can take proper decision about when to stop,

Fix missing denoise at the end of constant time render in Cycles X

A mistake since previous fix in the area, the denoiser is not always
scheduled: it can be deferred for later. So do proper state tracking
based on actual scheduled work.

Merge branch 'master' into cycles-x

Fix OpenGL context usage in Cycles X

Activating nullptr context is not a valid way to release the active
context, there is a dedicated function for this.

This also showed a logical error in the buffer mapping: the buffer
unmap is not supposed to release current OpenGL context but should
instead leave it active for a possible subsequent calls to the GPU
update. It worked before because the context as never released due
to wrong API usage.

Would say that the WM OpenGL API should have an assert to catch
such case, but this better to happen in the master branch.

Noticed while doing a further development related to GPUDisplay and
watching return value of GHOST_ActivateOpenGLContext.

Differential Revision: https://developer.blender.org/D11989

Cleanup: Remove unused Cycles X passes from list

Fix missing Noisy Shadow Catcher pass in Cycles X

Differential Revision: https://developer.blender.org/D11987