Add unit tests for VirtualizedList render quirks (#31401)

Summary:
This change adds a series of snapshot tests to validate the render output of VirtualizedList in mixed scenarios. Jest timer mocks are used to measure rendering at different ticks. These test cases mostly center around realization logic, to help prevent regressions when chaning internal state representation.
## Changelog

<!-- Help reviewers and the release process by writing your own changelog entry. For an example, see:
https://github.com/facebook/react-native/wiki/Changelog
-->

[Internal] [Added] - Add unit tests for VirtualizedList render quirks

Pull Request resolved: #31401

Test Plan: Ran the added UTs locally.

Reviewed By: lunaleaps

Differential Revision: D28017750

Pulled By: rozele

fbshipit-source-id: df9684c4ac80a8732f3e88e7496815127213832e