weston-agl-driver-conf: add recipe

weston-agl-driver-conf: add recipe

Add recipe which installs a systemd drop-in configuration override
to run Weston as the agl-driver user.  This will be used in the new
image for running agl-demo-control-panel, but may also be useful for
other downstream users.

Bug-AGL: SPEC-4952

Change-Id: I99c6801169e1c8e51a92c82fed354cdbbedda614
Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl-demo/+/29346
Tested-by: Jenkins Job builder account
Reviewed-by: Hiroyuki Ishii <ishii.hiroyuki002@jp.panasonic.com>
ci-image-boot-test: Jenkins Job builder account
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
ci-image-build: Jenkins Job builder account