feat: backpack throttling

[Kinerius]

What does this PR change?

• Limited the amount of Thumbnail that load concurrently to 10.

• Limited the number of Wearables that can be shown to 3 rows and X columns ( where X is based on the screen size )

• If the Wearables are higher than the limit that can be shown, pagination is shown.

• Merged NFTItemToggle prefab variants into one, the variance is now driven by skins defined by NFTItemToggleSkin ScriptableObjects

• Removed the CollectionContainer prefab as it has no purpose now, the base script still remains and its called ItemToggleContainer

• The ThumbnailManager manages the queue for the loading of the Textures, those textures are being cached and never get destroyed, we might have to limit or change this in the future.

How to test the changes?

• Open the backpack, and check that changing the resolution also changes the number of wearables that can be shown. (the shirts section is the one with the most wearables)
• Check that the pagination appears and disappears when changing wearable sections.
• Check that the pagination works correctly, and has sound feedback and subtle animations.

Our Code Review Standards

https://github.com/decentraland/unity-renderer/blob/master/docs/code-review-standards.md

[github-actions[bot]]

After the CI passes:

• This branch can be previewed at https://play.decentraland.zone/?renderer-branch=feat/backpack-throttling
• Code coverage report: https://renderer-artifacts.decentraland.org/branch-coverage/feat/backpack-throttling
• Benchmark report: https://renderer-artifacts.decentraland.org/branch-benchmark/feat/backpack-throttling/index.html

[Kinerius]

The gap issue should be fixed, also I've fixed the reparenting of all the explore UI so this fixes the initial hiccup

[RominaMarchetti]

@Kinerius this is looking amazing. There are still few to do:

• [x] The size of the numbers must be the same than the buttons randomize and done.
• [x] The font style must be Inter bold for all the numbers.
• [x] The color of the non selected numbers must be #161518
• [x] Adjust the pixels per unit in the image component of the white container for the arrow buttons. They look too rounded now. Try with a bigger number than 2 (2.5 or 3).

[Kinerius]

@RominaMarchetti can you recheck?

[RominaMarchetti]

@Kinerius the container of the arrows now doesn't look as rounded as it should be.

• [x] Check that the asset is Container12 and the pixel per unit 2.5, for both: arrows an numbers.
• [x] The highlight animation for the arrows is not consistent. The left arrow is ok considering it should just be a scale animation. Remove the color animation in the right arrow.
• [x] The margin between sections and items is not correct. Now there is a huge gap while it should be the same than in production.