Cleanup: GPUShader: Remove unused shaders

GPU: Add workaround for faulty default attrib values on some drivers

On some drivers, the default values is not respected correctly.

To workaround this we create a small VBO that contains only 1 vec4 worth of
data and just bind it using glBindVertexBuffer to ensure 0 stride.

This fixes T75069 Instances not rendered correctly by workbench.

Overlay: Fix crash caused by NULL passes

Fix T75087 Workbench: DoF: Divide By Zero when antialiasing is disabled

Overlay: Wireframe: New method to avoid zfighting with geometry

This new method is only enabled if Overlay Smooth Wire is enabled.

This method gives really nice results but has some downside:
- Require a depth copy or loose the ability to write wire depth to the
depth buffer and have correct depth ordering of wires. This patch use the former, with its associated cost.
- Require some depth sampling and prevent early depth test (i.e: has
some performance impact).
- Has some relatively minor instability with geometry that are perpendicular
to the view and intersecting with other geometry.

Pros:
- Compared to a fullpass approach this is surely going to have less
performance impact and much higher quality.
- Removes the additional vertex offset. (see T74961)
- Fixes all half edges z-fighting.

{F8428014}

{F8428015}

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D7233

Overlay: Wireframe: Make facing ratio offset depends on gl_Position.w

This makes the offset dependent of the actual near and far clip distances.

Fix T73505 EEVEE: Group output node sockets default value not working

This just cleanup the code and apply the expand to group output nodes.

Workbench: Fix default view not reset after drawing

This fix jitter of overlay and GPencil. But I'm not sure this should
be the responsibility of the subsequent draw engines or the responsibility
of the current engine to reset the view.

EEVEE: Update Preview file with new lightcache

EEVEE: Bump minimum probe level to make rough reflection more precise