Overlay Engine: Refactor & Cleanup

This is the unification of all overlays into one overlay engine as described in T65347.

I went over all the code making it more future proof with less hacks and removing old / not relevent parts.

Goals / Acheivements:
- Remove internal shader usage (only drw shaders)
- Remove viewportSize and viewportSizeInv and put them in gloabl ubo
- Fixed some drawing issues: Missing probe option and Missing Alt+B clipping of some shader
- Remove old (legacy) shaders dependancy (not using view UBO).
- Less shader variation (less compilation time at first load and less patching needed for vulkan)
- removed some geom shaders when I could
- Remove static e_data (except shaders storage where it is OK)
- Clear the way to fix some anoying limitations (dithered transparency, background image compositing etc...)
- Wireframe drawing now uses the same batching capabilities as workbench & eevee (indirect drawing).
- Reduced complexity, removed ~3000 Lines of code in draw (also removed a lot of unused shader in GPU).
- Post AA to avoid complexity and cost of MSAA.

Remaining issues:
- ~~Armature edits, overlay toggles, (... others?) are not refreshing viewport after AA is complete~~
- FXAA is not the best for wires, maybe investigate SMAA
- Maybe do something more temporally stable for AA.
- ~~Paint overlays are not working with AA.~~
- ~~infront objects are difficult to select.~~
- ~~the infront wires sometimes goes through they solid counterpart (missing clear maybe?) (toggle overlays on-off when using infront+wireframe overlay in solid shading)~~

Note: I made some decision to change slightly the appearance of some objects to simplify their drawing. Namely the empty arrows end (which is now hollow/wire) and distance points of the cameras/spots being done by lines.

Reviewed By: jbakker

Differential Revision: https://developer.blender.org/D6296

source/blender/gpu/intern/gpu_vertex_buffer.c

@@ -196,6 +196,19 @@ void GPU_vertbuf_attr_fill(GPUVertBuf *verts, uint a_idx, const void *data)
   GPU_vertbuf_attr_fill_stride(verts, a_idx, stride, data);
 }
 
+/** Fills a whole vertex (all attribs). Data must match packed layout.  */
+void GPU_vertbuf_vert_set(GPUVertBuf *verts, uint v_idx, const void *data)
+{
+  const GPUVertFormat *format = &verts->format;
+
+#if TRUST_NO_ONE
+  assert(v_idx < verts->vertex_alloc);
+  assert(verts->data != NULL);
+#endif
+  verts->dirty = true;
+  memcpy((GLubyte *)verts->data + v_idx * format->stride, data, format->stride);
+}
+
 void GPU_vertbuf_attr_fill_stride(GPUVertBuf *verts, uint a_idx, uint stride, const void *data)
 {
   const GPUVertFormat *format = &verts->format;