iox-#70 Fix clippy warnings

[elBoberido]

Pre-Review Checklist for the PR Author

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

Notes for Reviewer

This PR fixes all the clippy warnings.

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

• Closes Fix all clippy warnings #70

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 35.24590% with 79 lines in your changes missing coverage. Please review.

Project coverage is 49.83%. Comparing base (f7573d8) to head (55d6aee).

Files with missing lines	Patch %	Lines
iceoryx-sys/src/introspection/port.rs	0.00%	26 Missing ⚠️
iceoryx-sys/src/introspection/process.rs	0.00%	15 Missing ⚠️
iceoryx-sys/src/subscriber.rs	59.45%	15 Missing ⚠️
iceoryx-sys/src/introspection/memory.rs	0.00%	12 Missing ⚠️
iceoryx-sys/src/publisher.rs	57.69%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #71      +/-   ##
==========================================
- Coverage   50.77%   49.83%   -0.95%     
==========================================
  Files          20       20              
  Lines        1154     1202      +48     
==========================================
+ Hits          586      599      +13     
- Misses        568      603      +35     

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