[roll] Roll fuchsia Revert "[scenic] Delete kUp and kDown phases from InternalPointerEvent"

This reverts commit c63c7c6bbce2f439a1d91c9915f722317e57dd28.

Reason for revert: Broke A11yLegacyContender. Whoops.

Original change's description:
> [scenic] Delete kUp and kDown phases from InternalPointerEvent
>
> Removes support for legacy Up and Down phases from InternalPointerEvent
> now that legacy injection is gone. We instead add these phases back
> in for legacy clients before sending the events.
> This has the small side-effect of reordering when legacy focus events
> make it to the client. Where previously they would get ADD-FOCUS-DOWN
> they now get ADD-DOWN-FOCUS.
> This should be fine. No one should be relying on that specific behavior
> to begin with, and tap-focus is turned off on all products anyway.
>
> Edit: Uncovered a bug with how this was done previously where it
> wouldn't always end a contest at the correct time. With the
> faulty filtering logic in TouchSourceBase gone that particular
> failure mode is now impossible.
>
> Original-Fixed: 53316
>
> Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/734404

No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/736103
Original-Revision: edf5f84816084070d44b367ea2c7df7eea2eda4d
GitOrigin-RevId: cc9b41d835698df183c9aefee4b0ee341d8f4d27
Change-Id: Ieca15f532ee8bd3d0aadce6408ce32bb08249567