Add meta-stboot and systemd changes

meta-stboot/COPYING.MIT

meta-stboot/README

meta-stboot/conf/distro/poky-stboot.conf

meta-stboot/conf/layer.conf

meta-stboot/recipes-core/images/stboot-image.bb

...-stboot/recipes-core/packagegroups/packagegroup-stboot.bb

meta-stboot/recipes-core/stboot/stboot.bb

meta-stboot/recipes-core/stboot/stboot.inc

meta-stboot/recipes-core/stboot/stboot/finalize.sh

...stboot/recipes-core/stboot/stboot/host_configuration.json

meta-stboot/recipes-core/stboot/stboot/isrgrootx1.pem

...-stboot/recipes-core/stboot/stboot/ospkg_signing_root.pem

meta-stboot/recipes-core/stboot/stboot/trust_policy.json

meta-stboot/recipes-example/example/example_0.1.bb

meta/recipes-core/systemd/systemd_254.4.bb