Nodes: Add PixelationNode (#28802)

* sketched out draft of pixelation pass.

* Have normal and depth edges working

* Pixel size modifier

* playing with render targets

* fix renderTarget issue

* auto-mrt version of pixelation

* cleanup

* remove any outside tests, logs, and changes

* screenshot and cleanup

* more cleanup

* differentiate lighting from webgl version and modify to remove lighting errors

* final lighting adjustment

* Revert lighting

* bring back directionToColor

* fix screenshot

* filtering fix

* fix normalView and add new screenshot

* normalzie uvNodeNormal

* remove unused directionToColor import, floor widtth and height of resolution, change uniform naming to match other uniforms, fix comment spacing in updateBefore

* replace single expression tslFn function

* update lowerResolutionMaterial, remove unnecessary const color assignment

* revert to pixelationPass approach

* fix lint issue, ignore puppeteer test for now

* Update webgpu_postprocessing_pixel.html

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Co-authored-by: Michael Herzog <michael.herzog@human-interactive.org>