Rootfs: Move defconfigs to separate directory

Signed-off-by: Anton Kolesov <Anton.Kolesov@synopsys.com>
Rootfs: Use custom overlays for verification rootfs

Signed-off-by: Anton Kolesov <Anton.Kolesov@synopsys.com>
Rootfs: Add verification rootfs skeleton

Signed-off-by: Anton Kolesov <Anton.Kolesov@synopsys.com>
Rootfs: Add production defconfigs

Signed-off-by: Anton Kolesov <Anton.Kolesov@synopsys.com>