podman: Add support for blackhole routes

Add support for blackhole, unreachable, and prohibit route types in podman
networks. These route types allow silently discarding packets (blackhole),
rejecting with destination unreachable (unreachable), or rejecting with
administratively prohibited (prohibit).

Note: Blackhole routes require netavark >= 2.0.0. Regular unicast routes
remain backward compatible with all netavark versions.

Signed-off-by: Povilas Kanapickas <povilas@radix.lt>

<MH: Rebased atop latest main & fixed cherry-pick conflicts>

Signed-off-by: Matt Heon <matthew.heon@pm.me>