chore: move debugger tests in submodule (#3780)

# Description

## Problem\*

Resolves <!-- Link to GitHub Issue -->

## Summary\*

This PR just does some simple refactoring to make #3627's diff smaller.
Test functions are placed inside a submodule which then holds all of the
imports instead of them being in the functions themselves.

## Additional Context



## Documentation\*

Check one:
- [x] No documentation needed.
- [ ] Documentation included in this PR.
- [ ] **[Exceptional Case]** Documentation to be submitted in a separate
PR.

# PR Checklist\*

- [x] I have tested the changes locally.
- [x] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.