Update agl-kvm feature dependencies

Update agl-kvm feature dependencies

Add agl-demo-cluster-support and agl-demo-preload as dependencies
of the agl-kvm feature, as they are effectively required to get a
working agl-kvm-demo-platform image.

Bug-AGL: SPEC-5084

Change-Id: Ia766692f775e0274079ca266f4baf6e927bb6470
Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl-demo/+/29705
Tested-by: Jenkins Job builder account
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
ci-image-build: Jenkins Job builder account
ci-image-boot-test: Jenkins Job builder account
(cherry picked from commit cd3cbdd2638f51c009465d4e11d0405f81d4947f)
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl-demo/+/29759