[JENKINS-45050] Can only sort execution order when running sequential…

[Kanaduchi]

…ly #687

Decoupled matrix configuration sorting from sequential execution in the Matrix Project Plugin.

Previously, custom MatrixConfigurationSorter implementations were only applied when the "Run each configuration sequentially" option was enabled.

As a result, there was no way to control the execution order of matrix configurations while still running them in parallel.

What was fixed - Enabled matrix configuration sorting independently from sequential execution.

Testing done

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests that demonstrate the feature works or the issue is fixed