Because we know that the result of `try_parsing_as_integer` is
always going to be used to create a `DetectedConfiguration`, let's do
that directly, rather than requiring the caller to take an extra hop.

Previously, we had specs for the port priority spread out which made
it hard to change priority or add new items.

By extracting the priority to a single set of specs, it's clear
what the entire priority is, and there's a single place to change
and add to it.

This mirrors the same refactor that was done to the port specs:
rather than having the host spec priority specs spread out, we have
a single set of specs that validate the priority.