[roll] Roll fuchsia [audio][tests] Use FIFO barrier in plug detect test

Rework SimpleAudioTest.WatchPlugDetectAndCloseStreamBeforeReply
to avoid non-deterministic nanosleeps and OS thread spawning.

Instead, use asynchronous WireClients on a local async::Loop and
send a GetProperties request immediately after WatchPlugState.
Because Zircon channel messages are processed strictly in FIFO
order, receiving the GetProperties reply guarantees that the
preceding hanging get has been dequeued and registered by the
server thread prior to channel teardown.

This should improve flaky (inconsistent) test outcomes in highly
loaded test environments, such as asan-ubsan builds on arm64 EMU.

Test: fx test sa-unittest
Original-Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1676394
Original-Original-Revision: 63ecb7b37d8bbe064a1d7e83db7a6bcb51f52c5c
GitOrigin-RevId: b74420f1b4f779ef9f55a9628d4d4925f1acc5e2
Change-Id: I8dfe69cd22a70576cebe402172d8a9c19466126b
Reviewed-on: https://fuchsia-review.googlesource.com/c/integration/+/1685300
Cr-Commit-Position: refs/heads/main@{#195779}