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/GPU_shader.h

@@ -105,7 +105,6 @@ char *GPU_shader_get_binary(GPUShader *shader, uint *r_binary_format, int *r_bin
 typedef enum eGPUBuiltinShader {
   /* specialized drawing */
   GPU_SHADER_TEXT,
-  GPU_SHADER_TEXT_SIMPLE,
   GPU_SHADER_KEYFRAME_DIAMOND,
   GPU_SHADER_SIMPLE_LIGHTING,
   GPU_SHADER_SIMPLE_LIGHTING_FLAT_COLOR,
@@ -316,26 +315,8 @@ typedef enum eGPUBuiltinShader {
   /* lines */
   GPU_SHADER_2D_LINE_DASHED_UNIFORM_COLOR,
   GPU_SHADER_3D_LINE_DASHED_UNIFORM_COLOR,
-  /* light drawing */
-  GPU_SHADER_3D_GROUNDPOINT,
-  GPU_SHADER_3D_GROUNDLINE,
-  GPU_SHADER_3D_SCREENSPACE_VARIYING_COLOR,
-  /* bone drawing */
-  GPU_SHADER_3D_OBJECTSPACE_VARIYING_COLOR,
-  GPU_SHADER_3D_OBJECTSPACE_SIMPLE_LIGHTING_VARIYING_COLOR,
-  /* camera drawing */
-  GPU_SHADER_CAMERA,
-  /* distance in front of objects */
-  GPU_SHADER_DISTANCE_LINES,
-  /* axis name */
-  GPU_SHADER_3D_INSTANCE_SCREEN_ALIGNED_AXIS,
-  GPU_SHADER_3D_INSTANCE_SCREEN_ALIGNED,
   /* instance */
-  GPU_SHADER_INSTANCE_UNIFORM_COLOR,
-  GPU_SHADER_INSTANCE_VARIYING_ID_VARIYING_SIZE,    /* Uniformly scaled */
   GPU_SHADER_INSTANCE_VARIYING_COLOR_VARIYING_SIZE, /* Uniformly scaled */
-  GPU_SHADER_INSTANCE_VARIYING_COLOR_VARIYING_SCALE,
-  GPU_SHADER_INSTANCE_EDGES_VARIYING_COLOR,
   /* grease pencil drawing */
   GPU_SHADER_GPENCIL_STROKE,
   GPU_SHADER_GPENCIL_FILL,