feat: implements stable sorting

[drupol]

Fix #331

This PR:

• Fix [Feature request] Implement stable sorting #331
• Implements stable sorting (https://en.m.wikipedia.org/wiki/Sorting_algorithm#Stability)
• It breaks backward compatibility
• Is covered by unit tests
• Has static analysis tests (psalm, phpstan)
• Has documentation
• Is an experimental thing

[what-the-diff]

PR Summary

• Enabling Automatic Loading for New Directory
  The team has included one more directory named "fixture" to the autoload-dev section in our composer.json file. This is designed to automatically load certain classes during development for smoother workflow.

• Updated Documentation For Sorting Behavior
  They have added a new paragraph in our API documentation (api.rst) discussing the updated default behavior of data sorting starting from version 7.4. This provides our users with clear and up-to-date instructions on this functionality.

• Enhanced Sorting Functionality
  A modification has been made to our Sort.php file which improves our data sorting functionality. We can now support stable sorting, which maintains the relative order of items with equal sort keys. This should ensure that data remain in their original order even after being sorted.

• New File for Testing
  A new file MyValueObject.php has been added to the tests/fixtures directory. This object will aid in creating test scenarios and making sure everything runs as expected.

• Added Test Method for Sorting
  A new test method named testIssue331 has been added to our IssuesTest.php file. This test specifically checks the functionality of our new sorting feature utilizing the MyValueObject class. It helps ensure the sorting function runs smoothly and as expected.