Move music data inclusion into image instead of packagegroup and make it conditional

Move music data inclusion into image instead of packagegroup and make it conditional

This reworks the inclusion and moves conditional parts out of the packagegroup into the image definitions.
It also introduces a variable PREINSTALL_MUSIC that you can set to '1' in your conf/local.conf .

Bug-AGL: SPEC-5233
Change-Id: I3eaccfc1099c9d748d485fb144a77491d41af36d
Signed-off-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl-demo/+/30258
ci-image-build: Jenkins Job builder account
Tested-by: Jenkins Job builder account
ci-image-boot-test: Jenkins Job builder account
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl-demo/+/30216