[roll] Roll fuchsia [audio] Add ring buffer creation for virtual audio DAI

Also fix instance count to make it global.

Original-Bug: 124400
Original-Bug: 124865

Test: Add DAI virtual audio driver in one terminal with different
formats and in another run with no errors:
fx test audio_driver_tests -- --devfs-only --admin
After the audio_driver_tests run to completion pressing a key reports
no errors and the last format used.
$ fx shell virtual_audio --dai --add-format=0 --add --wait --get-format
...
--Received Format (44100 fps, 80 fmt, 2 chan, 0 delay) for output
$ fx shell virtual_audio --dai --add-format=1 --add --wait --get-format
...
--Received Format (96000 fps, 100 fmt, 4 chan, 0 delay) for output
$ fx shell virtual_audio --dai --add-format=2 --add --wait --get-format
...
--Received Format (48000 fps, 4 fmt, 2 chan, 0 delay) for output
$ fx shell virtual_audio --dai --add-format=3 --add --wait --get-format
...
--Received Format (16000 fps, 4 fmt, 2 chan, 0 delay) for outpu
$ fx shell virtual_audio --dai --add-format=4 --add --wait --get-format
...
--Received Format (96000 fps, 4 fmt, 2 chan, 0 delay) for output
$ fx shell virtual_audio --dai --add-format=5 --add --wait --get-format
...
--Received Format (48000 fps, 4 fmt, 3 chan, 0 delay) for output
$ fx shell virtual_audio --dai --add-format=6 --add --wait --get-format
...
--Received Format (8000 fps, 4 fmt, 1 chan, 0 delay) for output
$ fx shell virtual_audio --dai --add-format=7 --add --wait --get-format
...
--Received Format (48000 fps, 4 fmt, 1 chan, 0 delay) for output
$ fx shell virtual_audio --dai --add-format=8 --add --wait --get-format
...
--Received Format (96000 fps, 4 fmt, 2 chan, 0 delay) for output
$ fx shell virtual_audio --dai --add-format=0 --add --wait --get-format
...
Executing `--get-rb' command...
--Received SetBuffer (vmo size: 4096, ring size: 0, frames: 100, notifs: 0) for output

Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/841228
Original-Revision: 92e523f3960e727cc5f10257dafd1846d45b6349
GitOrigin-RevId: 18399264ec30bdadd5407249ea5a38f60b1cd80c
Change-Id: I513e983e94452c3d2ed80dc8658a7932298190fe