SL-18869, SL-18772  Overhaul VBO management, restore occlusion culling, intel compatibility pass, etc

Not supposed to happen, yet somehow did

Sl 18820: Build floater should preserve GLTF transforms when changing the PBR material

SL-18869 Touch up -- Prune "post_pos" from shadow shaders that don't need it and fix non-standard gl_Position z values

SL-18869 Optimizations -- Revive "Frame Profile" and GL_DEPTH_CLAMP.  Remove usage of gl_FragDepth from shadow shaders.

SL-18820: Fix applying material clearing transform overrides. Loosen some asserts to allow non-default transform overrides.

SL-18869 Optimizations -- Quiet command buffer -- VBO cache for UI et al and remove many unneeded VBO binds.

SL-18869 Optimizations -- LLVertexBuffer overhaul and shuffle of shadow map rendering to a place where the main camera has taken a stab at object updates for this frame before shadow map rendering has at them.

SL-18869 Optimizations -- Decruftify LLRenderTarget, use a shader to copy color/depth instead of glCopyTexSubImage or glBlitFrameBuffer

SL-18869 Optimizations -- Use _mm_prefetch to cut down on cache misses when iterating over render batches.

SL-18869 Optimizations -- decruftify LLVertexBuffer and make an optimal "renderShadowSimple" utility function for pushing vertex buffers only.

And cleaned up dupplicate mScale code

When in PBR 'mode', defaulted texture drops to diffuse channel

Fixes SL-18484.

SL-18780 Feedback cloud coverage into reflection probe ambiance to recover legacy behavior of cloud coverage brightening ambient lighting without destroying the ability to have good probe driven ambiance.