Rename fascist_firewall_* functions to reachable_address_*
In legacy/trac#17840 (moved) and legacy/trac#9067 (moved) / legacy/trac#9068 (moved), we unified ReachableAddresses and ClientUseIPv4/ClientUseIPv6/UseBridges. We'd previously unified FascistFirewall, FirewallPorts and ReachableAddresses.
This means that the functions called fascist_firewall_* should probably be renamed to be more descriptive.
I think reachable_address_* is one option, but let's follow typical naming standards and not repeat words in names:
- fascist_firewall_choose_address_dir_server ->
- reachable_address_choose_address_dir_server ->
Let's also use this as an opportunity to disambiguate fascist_firewall_choose_address_impl & fascist_firewall_choose_address_base.