services: set systemd list options as list values

This makes our list definitions mergeable with custom list values
set by users.
Previously, a module error ("value is a string while a list
was expected") was thrown instead.

This commit was partly auto-generated with this script:

#!/usr/bin/env ruby
Dir["**/*.nix"].each do |file|
  src = File.read(file)
  fixed = src.gsub(/ReadWritePaths *= *(.*?);/) do
    "ReadWritePaths = [ #{$1} ];"
  end
  File.write(file, fixed) if fixed != src
end

pkgs/lib.nix

@@ -46,7 +46,11 @@ let self = {
 
   # Allow takes precedence over Deny.
   allowLocalIPAddresses = {
-    IPAddressAllow = "127.0.0.1/32 ::1/128 169.254.0.0/16";
+    IPAddressAllow = [
+      "127.0.0.1/32"
+      "::1/128"
+      "169.254.0.0/16"
+    ];
   };
   allowAllIPAddresses = { IPAddressAllow = "any"; };
   allowTor = self.allowLocalIPAddresses;