[bug] properly write documentation for "trying omni" commands

[Unix4ever]

Previously we had talosctl cluster create qemu commands in 2 places: installation media, first start guide when no machines connected.
They were incorrect so we removed them.

We should bring them back but use the correct flags there:

1. The commands should have the correct schematic that will make the machines connect back to Omni when they are reset.
2. They should use the correct image factory URL.