Iox 5 add coverage

[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 CI job for test coverage and uploads the result to codecov.

To speed up the CI, the builds are now also cached and clippy reuses the build artifacts or a previous build.

Checklist for the PR Reviewer

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

Post-review Checklist for the PR Author

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

References

• Relates to #5

[codecov-commenter]

Codecov Report

:exclamation: No coverage uploaded for pull request base (master@d0813f9). Click here to learn what that means. The diff coverage is n/a.

@@            Coverage Diff            @@
##             master      #25   +/-   ##
=========================================
  Coverage          ?   38.97%           
=========================================
  Files             ?       17           
  Lines             ?     4180           
  Branches          ?        0           
=========================================
  Hits              ?     1629           
  Misses            ?     2551           
  Partials          ?        0           

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