feat: Use stack-allocated trait object

[gabyx]

Proposed Changes

• It is possible to create a wide-pointer to a trait object on the stack with newer Rust. This is possible because there is a feature called lifetime extension.
• Use this in the current code.

Types of Changes

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apply

• A bug fix (non-breaking change which fixes an issue).
• A new feature (non-breaking change which adds functionality).
• A breaking change (fix or feature that would cause existing
  functionality to not work as expected).
• A non-productive update (documentation, tooling, etc. if none of the
  other choices apply).

Checklist

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• I have read the
  CONTRIBUTING
  guidelines.
• I have added tests that prove my fix is effective or that my feature
  works.
• I have added the necessary documentation (if appropriate).

Further Comments

Something I learned at the RustFest. =)

[cmdoret]

Cool! This is also more readable 👍