Blender Git Loki

Change padding around checkboxes

Two changes:
* Reduce padding between checkbox and text. That makes it clearer what
the checkbox belongs to if there's also a column heading in front of
the checkbox.
* Don't add padding on the left side of checkboxes. That makes them line
up better with items above and below it.

Use row header for strip proxy resolutions

Use heading row for the Sequencer Flip X/Y controls

Use column header for Transform Affect Only toggles

Fix error in prior commit

Use new layout features throughout all Cycles properties

Better alignment in Experimental Preferences

Use checkbox+value for Sculpt Plane Trim & fix column headers

Fix expanded enums using columns within split layout

Fix expanded enums using columns within split layout

UI: Tweaks to modifier layouts

- Use checkbox + values configuration and expand 3-axis enums.

Merge branch 'temp-checkbox-layout-tweaks-patch' into temp-checkbox-layout-tweaks-apply

Merge branch 'temp-checkbox-layout-tweaks-patch' into temp-checkbox-layout-tweaks

Merge branch 'master' into temp-checkbox-layout-tweaks-patch

UI: Remove old hacks for dynamic scrollbar hiding

Although we still dynamically hide scrollbars, they don't change the
region size anymore. They are simply drawn on top of the region content.
Because of this, some hacks introduced by fa28e50ac2a7 are no longer
necessary.
Without these hacks, the scrollbar visibility is evaluated much more
often (cheap operation) which should be more reliable and possibly solve
some glitches.

Also replaces integers passed as booleans.

Fixes T75782.

GPencil: Change Y and U keys to use popovers

Instead to use the menus to change Layer and Materials, now the popover is displayed.

Merge branch 'blender-v2.83-release'

Fix T75675: Unlinking [with setting users to zero] not clearing
LIB_TAG_EXTRAUSER_SET flag

For example in the Image Editor, an assert would be triggered after
unlinking an image [with setting users to zero] and then setting the
image for the Image Editor again.

Whenever we set an Image for Image Editor, the Image ID is flagged
LIB_TAG_EXTRAUSER_SET, when we unlink [with setting users to zero] this
flag was not cleared.

quote @mont29: "a proper fix would be to move this to modern code, and
actually delete the ID..." but that is for later.

Maniphest Tasks: T75675

Differential Revision: https://developer.blender.org/D7452

Merge branch 'blender-v2.83-release'

Fix T75680: Nodegroup user count increased when file saved in edit group mode.

This editor's code was a bit schizophrenic, some parts considering its
nodetree usages as real refcounted ones, others, as shallow 'user one'
ones...

Editors should not be real ID users anyway, unless there are *very* good
reasons for it, so swich it to fully 'shallow' usage now.