Remove SDWebImage dependency

[guarani]

This proposes replaces usage of SDWebImage in the new MemoryCache following the comment #20956 (comment). It's only being used in one instance, to calculate the cost of objects added to the cache.

What's the difference between not passing in a cost and using sd_memoryCost? I'm not sure, so I'll share my current understanding and ask for feedback. For images, I don't see a difference because I think the cost is the image's size in bytes. For gifs (also UIImages), the cost calculation seems more complex since I think it's only the number of frames loaded into memory (not the frames that are kept on disk).

This PR is meant to start a conversation about which option to take: a. Let NSCache calculate the cost and remove SDWebImage from the Podfile b. Re-implement a cost calculation and remove SDWebImage from the Podfile c. Leave things as-is and close this PR

The assumption here is that by removing SDWebImage, we're not importing the library twice (once here and once in Gutenberg as a transitive dependency of a RN library).

To test: TO-DO

Regression Notes

1. Potential unintended areas of impact: TO-DO
2. What I did to test those areas of impact (or what existing automated tests I relied on): TO-DO
3. What automated tests I added (or what prevented me from doing so): TO-DO

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding unit tests for my changes.
• I have considered adding accessibility improvements for my changes.
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UI Changes testing checklist:

• Portrait and landscape orientations.
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• Fonts: Larger, smaller and bold text.
• High contrast.
• VoiceOver.
• Languages with large words or with letters/accents not frequently used in English.
• Right-to-left languages. (Even if translation isn’t complete, formatting should still respect the right-to-left layout)
• iPhone and iPad.
• Multi-tasking: Split view and Slide over. (iPad)

[guarani]

👋 @kean, would you be able to give me your thoughts on this as a follow-up to #20956 (comment)? The main thing I'm not sure about is what the value of the cache cost calculation that SDWebImage provides is.

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[kean]

@guarani I'd suggest going with option B and reimplementing the SDWebImage version: UIImage+MemoryCacheCost.m.

What's the difference between not passing in a cost and using sd_memoryCost?

If you don't pass the cost, it'll be 0 (only documented in the headers):

- (void)setObject:(ObjectType)obj forKey:(KeyType)key; // 0 cost

The cost must be non-zero in order for the totalCostLimit to work.

For gifs (also UIImages), the cost calculation seems more complex since I think it's only the number of frames loaded into memory (not the frames that are kept on disk).

SDWebImage also handles it, but we are not using images for rendering. The app caches original image data (Data). Gifu creates CGImage instances manually for each frame. These are not stored in our caches.

[kean]

I rebased it and updated cost calculation – ready for merge.

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[guarani]

Thanks @kean!