alsa-plugins: Add PACKAGECONFIG for libav, pulseaudio, jack

:Release Notes:
Support for jack was autodetected from sysroot.

:Detailed Notes:
Convert pulseaudio and libav to PACKAGECONFIGs, pulseaudio is in
DISTRO_FEATURES, because it's in default DISTRO_FEATURES_BACKFILL.

:Testing Performed:
Build tested only

:QA Notes:
No change in image

:Issues Addressed:
[GF-9365] Explicitly enable or disable autodetected dependencies
[ES-118] Evaluate possibility to build everything available in verification jobs

Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <martin.jansa@lge.com>
Change-Id: I00f45e0630e33112cc74472fef3a9f25b3dcdf25
Reviewed-on: https://g2g.palm.com/2844
Reviewed-by: Build Verification
Reviewed-by: Herb Kuta <herb.kuta@lge.com>
Reviewed-by: Martin Jansa <Martin.Jansa@lge.com>
Tested-by: Martin Jansa <Martin.Jansa@lge.com>
Reviewed-by: Susan Montooth <susan.montooth@lge.com>