Blender Git Loki

GPencil: Refactor: Make Texture UV transform behave like normal 3D ones

Meaning we apply location then rotation then scale. This makes positioning
using the parameters easier.

Also since the gradients now use the same UV space, we can reuse the same
properties for the transform.

GPencil: Fix vertex color draw tool color blending

This removes the darkened color artifacts due to incorect alpha blending.

GPencil: Refactor: Add fill vertex color suppport

This is a waste of GPU memory tho. It is duplicated for each gp points.

A better approach would be to store a per stroke data that we could fetch
using a stroke id.

GPencil: Rename mix_color to vert_color

Also renamed mix_color_fill to vert_color_fill

GPencil: Refactor: Enable Vertex color mode in vertex paint

This is to follow the same behavior as meshes.

GPencil: Refactor: Fix is_render flag

This should fix VFX toggling for render mode only.

GPencil: Refactor: Support solid mode color modes

This should be a 1:1 feature parity with what the workbench do with meshes
objects.

GPencil: Cleanup more unused code

GPencil: Remove unused variable

GPencil: Refactor: Make Lighting effect only happen in lookdev & render mode

This makes the lighting behavior much more consistent with the other objects.

Cleanup: GPencil: Remove unecessary comment

GPencil: Refactor: Fix depth sorting with workbench render

Cleanup: GPencil: Move shader static variable to gpencil_shader.c

GPencil: Refactor: Fix surface projected stroke not shown during stroke

GPencil: Replace tooltip

GPencil: Split overlay options in columns

GPencil: Remove Vertex Paint Opacity for Edi & Sculpt

GPencil: Remove duplicated code

GPencil: Refactor: Enable gpencil engine if xray is not used

Thus making the gpencil opaque. However, partial transparency is still
unsuported.

GPencil: Refactor: Remove 3D stroke offset

This is conflicting with overlays and makes objects poke through each
others. As the 3D mode is intended to 3D drawing, it should have correct
3D positionning. This will however create a lot of zfighting artifacts on
overlapping strokes.