Add dirs and symlinks property to filesystem

Dirs and symlinks will be created under the root of the filesystem.
Basic essential directories like "dev", "proc", "sys" and symlinks like
"bin -> /system/bin", "init -> /system/bin/init" can be created with
these properties.

Bug: 179652970
Test: boot with aosp_cf_x86_64_only_phone, see adb works
Change-Id: Ie06dc5a93635ea8b1e18be517ed8615b6c82fee6