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