sysutils/podman: Start unless-stopped containers on boot

[ahze]

Summary

The rc script only started containers with restart-policy=always.
Podman 5.8.0 added the should-start-on-boot filter, which also matches
unless-stopped containers that were not explicitly stopped by the user,
and 5.8.2 added podman stop --service so the service's own stop at
shutdown does not mark them as stopped by the user. Use both.

Approved by: dfr (maintainer), acm, dtxdf (mentors)

[ahze]

Test Plan: podman 5.8.6, FreeBSD 15.1. Three containers, then service podman onestop and onestart:

container	patched	before
unless-stopped	comes back	stays down
unless-stopped, stopped by hand	stays down	stays down
always	comes back	comes back