Replace router_should_skip_*() identifiers.

These identifiers are confusing and unreadable.  I think these
replacements should be better. Closes ticket #40012.

This is an automated commit, generated by this command:

./scripts/maint/rename_c_identifier.py \
        router_should_skip_orport_reachability_check_family router_orport_seems_reachable \
        router_should_skip_dirport_reachability_check router_dirport_seems_reachable \
        router_should_skip_dirport_reachability_check router_all_orports_seem_reachable