Issue #614 - update package imports

[nikosbosse]

Description

This PR closes #614.

This PR

• removes the lifecycle package from imports as we aren't using it anymore (at least for now)
• adds a version requirement to testthat as suggested in testthat version restriction for >=3.1.9 is required.  #614

On that note, we should maybe configure our R CMD check CI to fail when encountering a note. I think it currently let's Notes pass.

Checklist

• My PR is based on a package issue and I have explicitly linked it.
• I have included the target issue or issues in the PR title as follows: issue-number: PR title
• I have tested my changes locally.
• I have added or updated unit tests where necessary.
• I have updated the documentation if required.
• I have built the package locally and run rebuilt docs using roxygen2.
• My code follows the established coding standards and I have run lintr::lint_package() to check for style issues introduced by my changes.
• I have added a news item linked to this PR.
• I have reviewed CI checks for this PR and addressed them as far as I am able.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.27%. Comparing base (7df87d7) to head (4e15b71).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #723   +/-   ##
=======================================
  Coverage   95.27%   95.27%           
=======================================
  Files          21       21           
  Lines        1630     1630           
=======================================
  Hits         1553     1553           
  Misses         77       77           

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