Fix parallel testing databases

In rails#46270 it was reported that there were database errors when running
the tests in an app. I set up a demo app to use parallel testing and was
able to reproduce. The issue was that the `reconstruct_from_schema`
method needs to use the `pool` and not the `connection` because the
database might not exist yet and will raise an error. I don't know how
to test this inside Rails but I verified this behavior in my demo app.

Author: eileencodes

activerecord/lib/active_record/tasks/database_tasks.rb

@@ -384,7 +384,7 @@ def reconstruct_from_schema(db_config, format = ActiveRecord.schema_format, file
 
         check_schema_file(file) if file
 
-        with_temporary_connection(db_config) do
+        with_temporary_pool(db_config) do
           if schema_up_to_date?(db_config, format, file)
             truncate_tables(db_config)
           else