Workbench: Support Active Vertex Color

Currently it is not possible to view the vertex colors of an object. To
optimize the workflow, workbench will need to support Vertex Colors.

The Vertex Colors is a new option in `shading->color_type`. When objects
do not have vertex color, the objects will be rendered with the
`V3D_SHADING_OBJECT_COLOR`.

In order to support vertex colors in workbench the current texture/solid
shading structure is migrated to a primary shaders and fallback shaders.

Fix: T57000

Reviewers: brecht, fclem

Differential Revision: https://developer.blender.org/D4694

UI: Expand Enum Items Over Multiple Rows

Expanding enum items in a small area would render the names with
dots, what is a bad solution. When you use expand directly on a
`grid_flow` or `column_flow`, it will render the items on multiple
lines, giving more control to the developer.

Reviewers: campbellbarton, brecht, mont29

Differential Revision: https://developer.blender.org/D4698

Overlay Engine: Option to Disable AA Ortho Grid

When in Axis alligned orthographic view a grid was always displayed.
With this change the user can enable/disable this grid.

The Grid is always visible and editable, but only rendered active when user is in quad view, or axis aligned ortho view.

Reviewers: brecht, fclem

Maniphest Tasks: T63517

Differential Revision: https://developer.blender.org/D4699

Fix mistake in recent commit.

Needed to remove footers and not headers

Fix T63312: Crash XRay + clipping

Outline shaders were only selected when no checker depth was available.

Reviewed By: fclem

Maniphest Tasks: T63312

Differential Revision: https://developer.blender.org/D4661

Fix T62449: Subsurf+hidden faces

When using subsurf (and other modifiers) the edit flags are not
propagated correctly. Currently we assume to read the edit flags
from the original object which is kind off hinding the real issue.

Modifiers use `mesh_new_nomain_from_template_ex` to create a copy
from an existing mesh. this method is only used by modifiers. So
by placing this we will make sure that editmesh is propagated.

Reviewed By: fclem, sergey

Maniphest Tasks: T62449

Differential Revision: https://developer.blender.org/D4666

Mistake in 1be2888bf021

String compare renderengines.

EEVEE: Fix compilation

Introduced by f0d6879f5c7998be98ac406bd6ddaa5104961206

GPU not able to allocate texture

In the case of the report a GL_PROXY_TEXTURE_2D_ARRAY of 2509x2509x1 failed to be allocated.
This is a work around as the GL_PROXY_TEXTURE_* is not reliable.

Reviewed By: brecht, fclem

Maniphest Tasks: T63223

Differential Revision: https://developer.blender.org/D4651

Fix T63292: Crash Workbench Texture Drawing