iox-#5 Add RouDiEnvironment for testing

[elBoberido]

Pre-Review Checklist for the PR Author

1. [x] Code follows the Rust coding style and is formatted with rustfmt
2. [x] Branch follows the naming format (iox-#123-this-is-a-branch)
3. [x] Commits messages are according to this guideline
   • [x] Commit messages have the issue ID (iox-#42 commit text)
   • [x] Commit author matches Eclipse Contributor Agreement (and ECA is signed)
4. [x] Update the PR title
   • Follow the same conventions as for commit messages
   • Link to the relevant issue
5. [x] Relevant issues are linked
6. [x] Add sensible notes for the reviewer
7. [x] All checks have passed (except task-list-completed)
8. [x] Assign PR to reviewer

Notes for Reviewer

This PR adds a testing module with the RouDiEnvironment and a simple test which uses the RouDiEnvironment.

Further test will be added with a future PR since #23 will refactor the API.

Checklist for the PR Reviewer

• [x] Commits are properly organized and messages are according to the guideline
• [x] Code according to our coding style and naming conventions
• [x] PR title describes the changes

Post-review Checklist for the PR Author

1. [x] All open points are addressed and tracked via issues

References

• Relates to #5