feat: prohibit non-dns names for apps and process types

This is necessary for ensuring ssl certificates can be auto-retrieved for apps, and also easing integration into schedulers that use names and process types as part of DNS records.

As well, this fixes an issue where we may potentially have invalid DNS entries when adding apps to custom networks.

Closes #4102
Closes #4114

tests/unit/apps_1.bats

@@ -86,6 +86,11 @@ teardown() {
   echo "status: $status"
   assert_failure
 
+  run /bin/bash -c "dokku apps:create test_app"
+  echo "output: $output"
+  echo "status: $status"
+  assert_failure
+
   run /bin/bash -c "dokku --app $TEST_APP apps:create"
   echo "output: $output"
   echo "status: $status"