Split test running in CI

[KAUTH]

Description

• Split (fast) tests into 3 jobs
• Put slow tests in a separate job. If we start storing the test durations
  we won't need to do that probably.

Related to repository-service-tuf/repository-service-tuf#603

Fixes #(issue)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality not to work as expected)

Additional requirements

• Tests have been added for the bug fix or new feature
• Docs have been added for the bug fix or new feature

Code of Conduct

By submitting this PR, you agree to follow our Code of Conduct.

• I agree to follow this project's Code of Conduct

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.98%. Comparing base (25928b7) to head (5f5d49d).
Report is 20 commits behind head on main.

❗ Current head 5f5d49d differs from pull request most recent head 8653958. Consider uploading reports for the commit 8653958 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #519      +/-   ##
==========================================
+ Coverage   98.97%   98.98%   +0.01%     
==========================================
  Files          14       14              
  Lines         588      594       +6     
==========================================
+ Hits          582      588       +6     
  Misses          6        6              

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