Fix T67587: Fix Drawing in Wireframe Non X-Ray Mode

When using Vertex or Weight paint mode on a wireframe the overlay was
blended with the background. In this case we now use alpha blending.

Reviewed By: fclem

Differential Revision: https://developer.blender.org/D5340

Fix T67638: Stretched Camera Background Images

The matrices that projects background images in the 3d view
were incorrect. The root cause was that the coordinate systems were not
respected, that was most noticeable when rotating a stretched image.

We re-validated conversions of coordinate spaces (UV -> Image -> Camera -> Window)
and made sure that the rotation is done in image space.

Reviewed By: campbellbarton

Differential Revision: https://developer.blender.org/D5431

DrawManager: Fixed Assertion In Workbench

Fix T66100: WorkBench Banding Issues

Color banding issues can appear, as result of the 8 bitdepth RGBA that
is used in the viewport.

This change will use `GPU_RGBA16F` for final renderings and for drawing textures. This
allows displaying HDRI textures. Vertex Colors uses `GPU_RGBA16` to resolve
color banding issues. All other modes use `GPU_RGBA8` to reduce
bandwidth and gpu memory.

Reviewed By: fclem, brecht

Differential Revision: https://developer.blender.org/D5179

Fix T66671: Memory Leak Material Preview

During generating of a material preview with world lighting only the
copy world was being freed. The material was removed from the main, but
was not freed.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D5224

DrawManager: Fix Camera Images Interfere During Selection

When drawing the selection buffer the camera images were drawn. This
resulted in unneeded extra clicking for the user. This change will
ignore camera images during the selection.

Reviewed By: fclem

Differential Revision: https://developer.blender.org/D5276

Refactor Paint Overlay Opacity Panel

It is now possible to translate this panel. Due to the previous
structure the translation tools were not able to pick the strings up as
translatable strings.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D5279

Fix T67437: Vertex Colors Not Visible In SculptMode

Recently Shader parameter names for UVMaps and vertex colors were renamed.
The sculpt drawing code still used the old parameter names.

Reviewed By: fclem

Differential Revision: https://developer.blender.org/D5320

Fix: Cycles reporting incorrect number of samples in viewport render

During viewport rendering where the viewport samples are set to 0 the UI
showed 16777216 as number of samples. We should not show the number of
samples when the number of viewport samples are set to 0.

Differential Revision: https://developer.blender.org/D5301

Fix T67105: Missing Update Add Camera Background Image

Reviewed By: brecht, sergey

Differential Revision: https://developer.blender.org/D5284