Also tweak our vignette to help (further) skip samples we don't need, and for further look and feel adjustments.
SL-19784

SL-19784

SL-19784

SL-19784

SL-19808: Fix orientation of PBR normal texture when texture transform and/or texture animation is applied

DRTVWR-559 Revert skies to be very close to release and disable tone mapping when probe ambiance is zero.

Hack for desaturating legacy materials has been removed for performance and quality reasons.

Adds a new setting for auto adjusting legacy skies.  This is the PBR "opt out" button.  If disabled, legacy skies will disable tonemapping, automatic probe ambiance, and HDR/exposure.  If enabled, legacy skies will behave as if probe ambiance and HDR scale are 1.0, and ambient will be cut in half.  

HDR scale will act as a sky brightener, but will automatically adjust dynamic exposure so the sky will be properly exposed.  If you want relatively even exposure all the time, set HDR Scale to 1.0.  If you want a high range of exposures between indoor/dark areas and outdoor/bright areas, increase HDR Scale.

Also tuned up SSAO (thanks Rye!).

Reviewed with Brad.

DRTVWR-559
DRTVWR-583

SL-19713 Fix for broken avatar preview render in animation upload.  Incidental decruft and camera FoV network spam reduction.

* Fix water fog mismatch between alpha blend and opaque when local light is nearby

* Add PBR underwater alpha blend shader

DRTVWR-559 Remove RenderReflectionProbeCount (which is bugged) and lean on RenderReflectionProbeLevel for preferences (which works).

DRTVWR-583
DRTVWR-559

DRTVWR-583

SL-19709 Fix for fullbright shiny not factoring out exposure and flickering fullbright alpha.  Incidental decruft.

DRTVWR-583

DRTVWR-559 Add "No Post" mode and refactor "Scene Gamma" into "Brightness" for adjusting legacy gamma when probe ambiance is 0 and dynamic exposure when probe ambiance is not zero.

SL-19560 Revert hacky fix for other avatars having low res BoM textures.  Fix for brightening of PBR materials at the shadow horizon.

DRTVWR-559 Add control for automatic reflection probes to advanced preferences and featuretable. Remove Reflections checkbox.  Don't persist reflection probe volume display between sessions.  Incidental decruft.

TODO: Why did this work for the equivalent non-rigged prim?