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.

SL-18852 Refactor GLTF material rendering to not be special compared to other types.  Hook GLTF alpha masking up to highlight transparent.

Apparently Visual Studio and Xcode disagree on the intended lifespan of a
certain temporary expression. Capturing it in a named variable works.

Attempt to restore SL-17823 fix after merge with DRTVWR-559 texture pipeline work removed the getDecodePriority() method.

Was a placeholder when there was no other way to bring it up