Feat: Noise and Blur filters for Canvas

[dunkeroni]

Summary

A few things lumped together here.

1. Image Blur invocation now correctly handles transparent regions instead of darkening edges.
   Old method: (center and right image will look the same if your git is not in Dark Mode, but the right image has a white background)
   
   New method:
   

2. Paste Image node now respects transparency. Previously alpha channel of the top image would override the bottom.

3. Added Image Noise invocation to introduce random noise into images. Supports gaussian/salt-and-pepper modes in greyscale/color.
   

4. Created filters in Canvas for blur and noise to improve img2img results.
   

noise_filters_2.mp4

Above video was taken before Noise Size input was added.

Related Issues / Discussions

Additional noise strategies possibly to be added later on:

• Worley/Voronoi have interesting implications, but may not be useful for canvas.
• Image diffusion noise might result in more consistent img2img results at the risk of decreased improvement.
• Simplex noise patent ran out in Jan 2022 (may be slower/worse than OpenSimplex2?)
• Perlin noise might be helpful for organic textures

Known Issues (not from this PR, but visible because of it):

• Blur filter does not have intended results when used on a cutout/brushed shape layer. Layers are cropped to only the visible pixels, and filters cannot change the size of a layer. Adding that capability will require changes to how the canvas handles new raster layers.
  
• Filter previews show the original image behind the filtered version, which makes previewing a blur filter difficult.
  

Merge Plan

Ready to merge

Checklist

• The PR has a short but descriptive title, suitable for a changelog
• Tests added / updated (if applicable)
• Documentation added / updated (if applicable)
• Updated What's New copy (if doing a release after this PR)

[psychedelicious]

Thanks! I've pushed 3 commits:

• Run make ruff to fix python style checks.
• Run make frontend-typegen to update the frontend generated typescript types.
• Hide the layer being filtered when rendering the preview, which fixes that transparency issue.

I also thought about the issue where the blur gets cut off by the layer bounds but I still don't have an easy fix for that, will probably need some deeper fiddling to sort.