Blender Git Loki

Cleanup: tweak Freestyle #includes in preparation for clang-format sorting

Cleanup: Fix forward declaration of headers

Cleanup: Rename ARegion variables from ar to region

The old convention was easy to confuse with ScrArea.
Part of https://developer.blender.org/T74432.

This is mostly a batch rename with some manual fixing. Only single word
variable names are changed, no prefixed/suffixed names.

Brecht van Lommel and Campbell Barton both gave me a green light for
this convention change.

Also ran clan clang format on affected files.

Cleanup: Image: Move to IDTypeInfo and remove unused BKE API.

Cleanup: Texture: Move to IDTypeInfo and remove unused BKE API.

Cleanup: Material: Move to IDTypeInfo and remove unused BKE API.

Fix build error on windows

```
Error C4013 '_VA_ELEM1' undefined; assuming extern returning int
```

Cleanup: Action: Move to IDTypeInfo, and remove unused BKE API.

Cleanup: Armature: Move to IDTypeInfo, and remove unused BKE API.

Bring back code accidentally removed by previous commit

Probably got lost when resolving merge conflicts.

Cleanup: Reduce context usage in UI functions

Part of https://developer.blender.org/T74429.

There's a chance that this causes some issues becaue in some cases we
change from getting the window from context to getting it from somewhere
else.

Cleanup: Lattice: Move to IDTypeInfo and remove unused BKE API.

Cleanup: MetaBall: Move to IDTypeInfo and remove unused BKE API.

Cleanup: Curve: Move to IDTypeInfo and remove unused BKE API.

Cleanup: Mesh: Move to IDTypeInfo and remove unused BKE API.

Cleanup: move Alembic, AVI, Collada, and USD to `source/blender/io`

This moves the `alembic`, `avi`, `collada`, and `usd` modules into a common
`io` directory.

This also cleans up some `#include "../../{somedir}/{somefile}.h"` by
adding `../../io/{somedir}` to `CMakeLists.txt` and then just using
`#include "{somefile}.h"`.

No functional changes.

Depsgraph: remove unused no-op nodes after building

This is the companion of D7031. That patch adds a new DIMENSIONS node to
the depsgraph for each object that has geometry. However, this node is
only necessary when there are drivers using an object's dimensions as
variable. Since this is rare, it's easiest to remove these nodes after
they turn out to be unnecessary. This is what (almost) happens in this
patch.

Removing nodes from the depsgraph is hard, and there are no functions to
do this yet. Instead, this patch recursively removes all the incoming
relations from unused no-op nodes (i.e. no-op operation nodes without
outgoing connections). Actually removing the nodes will be left as a
future improvement.

I've tested this on a Spring file [1]. Here are there results of blender
--debug-depsgraph-time spring_02_055_A.eevee.blend and letting it run
for a while to stabilise the reported FPS:

master: 11.7 FPS
Just D7031: 11.7 FPS
Just D7033: 11.8 FPS
Both D7031 + D7033: 12.3 FPS

[1] https://cloud.blender.org/p/spring/5d30a1076249366fa1939cf1

Differential Revision: https://developer.blender.org/D7033

Cleanup: Move Multiplane Scrape brush to its own file

Fix narrowing from int to short when removing material slot

Sculpt: Cleanup, remove macro re-definition