Summary:
A CellRenderMask helps track regions of cells/spacers to render. It's API allows adding ranges of cells, where its otput be an ordered list of contiguous spacer/non-spacer ranges.
The implementation keeps this region list internally, splitting or merging regions when cells are added. This output will be used by the render function of a refactored VirtualizedList.
## Changelog
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[Internal] [Added] - Add "CellRenderMask" Region Tracking Structure
Pull Request resolved: https://github.com/facebook/react-native/pull/31420
Test Plan: Validated via UTs.
Reviewed By: lunaleaps
Differential Revision: D28293161
Pulled By: rozele
fbshipit-source-id: a5e4e2144a90387aabe0974650429018440abf67
Nick Gerleman