Ensure Kotlin Curriculum is 'Hosted Environment Ready'

[davidmillican]

Instructions on how to get the most out of our setup are found in this README section in Notion, with
helpful comments exercise_config_template.yaml in the curriculum repo.

In order to switch the hosted environment fully on, we need to check it is ready for all
curricula, and that coaches will not be confused by the behaviour. This means simple
setup (ideally just one click to open the environment with no further setup steps).

Some examples of where this is currently working:

• The EC2 Exercise Config
• The Core SQL Exercise Config

There are instructions on how to test an HLE configuration in this Notion page, but let
Dave know if you have any difficulty.