Modifiers: Add option to directly specify a 2D transform for UVWarp

Currently the only option is to warp based on the transform of other
objects, which is inconvenient if you want to e.g. control it through
a driver - you need to set up a dummy object and go through that,
which is clunky and should be unneccessary.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D6690

Freestyle: Add option for rendering Freestyle to a separate pass

This allows for more flexibility in Compositing compared to the
hardcoded alpha-over that is currently used.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D6829

Merge branch 'blender-v2.82-release'

Fix unreported: Packing/unpacking errors don't mention tiled images

Thanks to @dfelinto for spotting this!

Fix T73713: Tiled textures (UDIM) getting lost when saving the .blend but not the textures

The issue here is simple, IMA_SRC_TILED was missing from a check for whether the image should
be saved.

Note that tiled images won't be automatically saved if they have never been saved before.
For single images this is handled by packing them, but packing of tiled images isn't
supported yet.

However, in that case the file closing dialog will at least show a warning now instead of
completely ignoring tiled images.

Cycles: Track specular throughput to account for reflection color in denoising albedo pass

To determine the albedo pass, Cycles currently follows the path until a predominantly
diffuse-ish material is hit and then takes the albedo there.
This works fine for normal mirrors, but as it completely ignores the color of the bounces
before that diffuse-ish material, it also means that any textures that are applied to the
specular-ish BSDFs won't affect the albedo pass at all.

Therefore, this patch changes that behaviour so that Cycles also keeps track of the
throughput of all specular-ish closures along the path so far and includes that in
the albedo pass.

This fixes part of the issue described in T73043. However, since it has an effect on the
albedo pass in most scenes, it could cause cause regressions, which is why I'm uploading
it as a patch instead of just committing as a fix.

Differential Revision: https://developer.blender.org/D6640

Merge branch 'blender-v2.82-release'

Fix unreported: Trying to create invalid UDIM tiles failed without error

Thanks to @dfelinto for spotting this!

Fix unreported: View All in the Image Editor ignores UDIM tiles

Thanks to @dfelinto for spotting this!

Merge branch 'blender-v2.82-release'