feat(rust/systemd): Implement systemd-tmpfiles, timedatectl, and systemd-creds for integration tests
Add comprehensive systemd-tmpfiles support: config file precedence with global
filename sorting, path dedup, C-style path/content unescaping, age-by timestamps,
x/X exclude patterns, ':' create-only modifiers, '$' purgeable and '?' conditional
modifiers, L+/C default factory paths, --purge flag, POSIX ACL support via setfacl,
os-release specifier expansion (%o/%B/%W/%w/%M/%A), and --root-aware symlink targets.
Extend timedatectl with set-local-rtc and NTP status support. Extend systemd-creds
with list and cat subcommands. Add acl package to test VM.
Passes TEST-22-TMPFILES, TEST-45-TIMEDATE, and TEST-54-CREDS integration tests.
Signed-off-by: Niclas Overby <niclas@overby.me>