WebGPUPathTracer: Use custom float texture filter

[gkjohnson]

Relies on #748
Replaces #749

• Add an ssl option to the start command to allow for testing on mobile (WebGPU requires https) - run npm start -- --mode=ssl --host
• Adjust the ProceduralEquirectTexture to use HalfFloatType to guarantee its filterable.
• Add custom linear filtering when rendering to the screen
• Switch the render target 2d array to use MeshBasicMaterial rather than render to screen material

There seem to be some issues in three.js regarding setting float textures to unfilterable so in practice this won't work on mobile until this is fixed: mrdoob/three.js#33147

cc @TheBlek