Experimental VirtualList Optimization (#27115)

[lunaleaps]

Summary:
This is VirtualList Optimization done by christianbach in #21163 enabled behind a prop: experimentalVirtualizedListOpt with backward compatibility.

Fixes #20174 based of jasekiw pull request #20208

Changelog

// TODO:

[CATEGORY] [TYPE] - Message

Pull Request resolved: #27115

Test Plan:
// TODO:
Add tests related to backward compatibility. (Will need help)

Differential Revision: D30095387

Pulled By: lunaleaps

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This pull request was exported from Phabricator. Differential Revision: D30095387

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	Messages
📖	📋 Verify Changelog Format - A changelog entry has the following format: [CATEGORY] [TYPE] - Message. CATEGORY may be: General iOS Android JavaScript Internal (for changes that do not need to be called out in the release notes) TYPE may be: Added, for new features. Changed, for changes in existing functionality. Deprecated, for soon-to-be removed features. Removed, for now removed features. Fixed, for any bug fixes. Security, in case of vulnerabilities. MESSAGE may answer "what and why" on a feature level. Use this to briefly tell React Native users about notable changes.
📖	📋 Missing Test Plan - Can you add a Test Plan? To do so, add a "## Test Plan" section to your PR description. A Test Plan lets us know how these changes were tested.
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Generated by 🚫 dangerJS against bd4bdfc

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Platform	Engine	Arch	Size (bytes)	Diff
ios	-	universal	n/a	--

Base commit: 8a8a532

[azizhk]

Ah, I see. I love this approach. 😍 Less Nesting, Less Props.

Just that now in the same tree, you can't have two versions of VirtualList one with optimization and one without. (Which I am totally fine with)

[halaei]

In case you are interested, take a look at #31327 as well. I hope it is relevant. Thanks.

[lunaleaps]

Ah, I see. I love this approach. 😍 Less Nesting, Less Props.

Just that now in the same tree, you can't have two versions of VirtualList one with optimization and one without. (Which I am totally fine with)

Mm that's a good point. I think since this is a question of optimizing overall that's a fine tradeoff. We'll want to run an experiment internally.. to be honest I'm not sure I understand the optimization... might have to scan the issue history a bit more closely or if you could give me TL;DR?

I'll re-post this on the original PR and we can continue discussion there.