Add agl-kuksa-val feature

Add agl-kuksa-val feature

Add feature for pulling in meta-agl-kuksa-val layer, and extend
AGL_FEATURES to indicate its presence.

Bug-AGL: SPEC-5299

Change-Id: Ie30e818413f2fc9d87926c655abe1310469e3979
Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/30532
ci-image-build: Jenkins Job builder account
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
Tested-by: Jenkins Job builder account
ci-image-boot-test: Jenkins Job builder account