[roll] Roll fuchsia Revert "[starnix] Avoid syscalls for starnix-backed FD events"

This reverts commit 4bcd5865e131b49caa3e491bf10ccc47e7f71041.

Reason for revert: tree closure due to starnix build failure

Original change's description:
> [starnix] Avoid syscalls for starnix-backed FD events
>
> Previously, events on FDs that are implemented purely in starnix (e.g.
> pipe, eventfd, netlink sockets) each triggered a unique `zx::UserPacket`
> on a `zx::Port` (which backs a starnix `Waiter`). This meant that a
> `Waiter` may perform `O(N + M)` Fuchsia syscalls to collect all of the
> ready events to pass back to starnix user-space (where N is the number
> of FDs backed by pure starnix implementations and M is the number of FDs
> backed by the Fuchsia platform (e.g. network sockets)).
>
> This change introduces an in-starnix queue of pending events for FDs
> backed by pure starnix implementations, replacing the need for a
> per-event `zx::UserPacket`. Now, we only use a single `zx::UserPacket`
> to wake up a `Waiter` regardless the number of pending events for FDs
> backed by pure starnix implementations. This results in a `Waiter`
> performing only `O(M)` Fuchsia syscalls to collect all of the ready
> events to pass back to starnix user-space.
>
> Note that this CL changes the ordering semantics of triggered events by
> batching all user events with the first pending user event. There does
> not seem to be anything documenting any specific ordering so this CL
> reordered events to gain some performance wins when operating on FDs
> backed by starnix. Concretely, if events were triggered in the following
> order:
>   - network socket (Fuchsia)
>   - eventfd (starnix)
>   - filesystem (Fuchsia)
>   - pipe (starnix)
>   - netlink socket (starnix)
>
> The events will be returned in the following order:
>   - network socket (Fuchsia)
>   - eventfd (starnix)
>   - pipe (starnix)
>   - netlink socket (starnix)
>   - filesystem (Fuchsia)
>
> An alternative design was considered where the waiter implementation
> will eagerly check the in-starnix queue and only check the `zx::Port`
> if the in-starnix queue was empty, but this was abandoned as it allows
> for the edge-case where events triggered by the Fuchsia platform are
> never handled when starnix is constantly triggering events and keeping
> the in-starnix queue of events hydrated. The current implementation
> still relies on a `zx::UserPacket` enqueued to the `zx::Port` to
> determine when we dequeue from the in-starnix queue or process an event
> from the Fuchsia platform, avoiding the starvation problem.
>
> FUTURE: Another optimization that would help more generally is to
> introduce a variant of `zx_port_wait` that supports batch reading of
> `zx_port_packet_t`s. See https://fxbug.dev/134622.
>
> Performance Wins:
> ```
> Test case                                               Improve/regress?  Factor change  Mean before           Mean after
> ------------------------------------------------------  ----------------  -------------  --------------------  --------------------
> fuchsia.starnix.gvisor_benchmarks: EpollAllEvents/1024  improved          0.549-0.598    2315600 +/- 40512 ns  1326480 +/- 33901 ns
> fuchsia.starnix.gvisor_benchmarks: EpollAllEvents/2     improved          0.853-0.899    7423 +/- 122 ns       6500 +/- 63 ns
> fuchsia.starnix.gvisor_benchmarks: EpollAllEvents/512   improved          0.542-0.606    1150627 +/- 15511 ns  660076 +/- 28365 ns
> fuchsia.starnix.gvisor_benchmarks: EpollAllEvents/64    improved          0.569-0.614    143408 +/- 2117 ns    84762 +/- 1997 ns
> fuchsia.starnix.gvisor_benchmarks: EpollAllEvents/8     improved          0.675-0.710    20674 +/- 177 ns      14314 +/- 238 ns
> ```
>
> Original-Bug: 134622
> Original-Bug: b/296273285
> Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/924718

Original-Bug: 134622
Original-Bug: b/296273285
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/925174
Original-Revision: bcd8df5a656f5d26486f9633982da20541d76951
GitOrigin-RevId: 318b050ef4d53c73791e05ecb1050bc8b5fda3b8
Change-Id: I7cf744b9ab98bffb7b76d263177a20b8807c9b19