chore(preprod): Add AssetCatalog Parsing support for Multisize sets

[NicoHinderling]

Certain assets weren't getting picked up for the Firefox app, and the ones missing appeared to be multisize sets, like this

    {
        "vector": false,
        "type": 0,
        "imageId": "42D31467-E63B-49D8-8D9B-1B608059E344",
        "size": 236,
        "height": 1024,
        "name": "AppIcon_Alt_Color_Purple",
        "filename": "AppIcon_Alt_Color_Purple",
        "idiom": "phone",
        "width": 1024
    },

They won't have a a file extension either it seems (ex. Assets.car/AppIcon_Alt_Color_Purple). So we'll go ahead and save them as a (default type) png

[NicoHinderling]

@trevor-e #2859 (comment)

I know you previously mentioned that we should be defensive and not include images missing a file type but in this case we want to include some that indeed don't have one

[trevor-e]

We can keep the old defensive logic if we restructure this a bit:

if 
  unslicedImage == nil && className == "_CUIThemeMultisizeImageSetRendition", 
  let result = findImageForMultisizeSet(rendition, key, assetKeys, structuredThemeStore) {
    unslicedImage = result.image
    width = result.width
    height = result.height
    images[imageId] = (cgImage: unslicedImage, format: "png")
} else !fileExtension.isEmpty && fileExtension != "svg", let unslicedImage = unslicedImage {
    images[imageId] = (cgImage: unslicedImage, format: fileExtension)
}

[trevor-e]

We can keep the old defensive logic if we restructure this a bit:

if 
  unslicedImage == nil && className == "_CUIThemeMultisizeImageSetRendition", 
  let result = findImageForMultisizeSet(rendition, key, assetKeys, structuredThemeStore) {
    unslicedImage = result.image
    width = result.width
    height = result.height
    images[imageId] = (cgImage: unslicedImage, format: "png")
} else !fileExtension.isEmpty && fileExtension != "svg", let unslicedImage = unslicedImage {
    images[imageId] = (cgImage: unslicedImage, format: fileExtension)
}

[trevor-e]

Making this mutable and then later on depending on unslicedImage to be nil for the findImageForMultisizeSet() feels weird to me. Is there something more stable we can check to see if it's a multisize set, like the type? Similar to how we do let isVector = type == 9

[trevor-e]

Like I figured this would be structured like:

if isMultisizeImageSet {
 // logic
} else {
  // old logic
}