Update Section: Testing

This section is already pretty up to date, looks like someone went over it recently with the RFC-232 changes.

Some things to add:

- [ ] explanation for why the types of tests introduced in the guides go in directories with legacy names (acceptance, integration).
- [ ] explanation of why both Unit Tests and Container Tests both go in the unit directory.
- [ ] examples of nesting modules. (A module within a module).
- [ ] explanation of how to stub/mock a method or object in a unit or container test.
- [ ] mention addons that could help with testing
- [ ] testing routes: include how to handle testing the asynchronous beforeModel, model, or afterModel hooks.
- [ ] how to test Query Params
- [ ] how to test Native ES Classes
- [ ] What to do if you get the "autorun is disabled, wrap in a run loop" error message?