Summary:
Scroll views set up with an inverted vertical axis can't support view flattening due to the flattening not taking the axis inversion in consideration while repositioning the views.

This diff disables view flattening on the cells of the virtualized list so that the layout would be correct in inverted scroll views when using Fabric.

The change is not being applied to ScrollView directly because we can safely assume that vertical axis inversion will only be enabled on VirtualizedList/FlatList.

Test Plan:
Run Zeratul with Fabric and check that the vertical order of grouped bubble messages is correct.

| Before | After |
|--|
|  {F1136386200}  |  {F1136386364}  |

Reviewers: shawndempsey, #rn-desktop

Reviewed By: shawndempsey

Differential Revision: https://phabricator.intern.facebook.com/D50846483

Tasks: T167539420

…ents of VirtualizedList

Summary:
View flattening was already disabled in the cell renderer used by the Virtualized List in this diff D50846483

This diff disables view flattening in the header, footer, empty and spacer cells to fix the layout being broken because of the vertical axis flipping used by the reverse order virtualized list.

Test Plan:
Run Zeratul with Fabric enabled and scroll to the top of a message thread to show the participants summary header.

| Before | After |
|--|
|  {F1145726580}  |  {F1145726618}  |

Reviewers: shawndempsey, chpurrer, #rn-desktop

Reviewed By: chpurrer

Differential Revision: https://phabricator.intern.facebook.com/D51182545

Tasks: T167539420