The /reload command doesn't reload the test_instance registry, requiring a server restart in order to detect changes in this registry. I expected the /reload command to reload the test_instance registry so I don't have to restart the server when I change the datapack.

Steps to reproduce:

1. Open a world
2. Add a test instance to the test instance registry in a datapack
3. Run the /reload command
4. Observe that the new test instance isn't registered

This also affects existing test instances which are modified.