DOF improvements

Possible improvements for DOF implementation here

Features:

• WebGPU support. There is compilation issue with one shader currently due to glslang adding no longer supported keyword to the WGSL shader. The solution is to write a version of the shader directly in WGSL. https://github.com/playcanvas/engine/pull/7218
• update CameraFrame script to expose this functionality to the Editor
• physically based bloom, where instead of distance and range parameters, the bloom is controlled by camera parameters: aperture, fov)
• blur green channel of CoC texture to allow near blur objects to have soft edges

Performance / quality:

• make the near blur optional, for experiences where only the background needs to be blurred https://github.com/playcanvas/engine/pull/7220
• when only a small amount of blur is used (less than about 3), it's more obvious the half res scene texture is used as a blur source. We could use high res at that point at a higher cost.
• use compute shaders as described in links from the original PR to generate tile min/max CoC textures and dispatch more appropriate (cheaper) blur shaders for individual tiles.
• when TAA is used at the same time, the blurred background flickers due to TAA jitter. We could try to influence TAA's strength based on CoC texture - limit TAA in the more blurry regions. Can be slight perf win as well.
• consider generation of few (2-3) mip levels of the scene texture (currently have half res only), and optimize the sampling algorithm to use lower mips for wider blurs, with less samples.