feat: add comprehensive test coverage for ProcessDetails entity class (#6590)

* feat: add comprehensive test coverage for ProcessDetails entity class (#6588)

- Add ProcessDetailsTest.java with 20 comprehensive test methods
- Cover all constructors, getters, and setters
- Include edge cases: null values, negatives, zeros, max values
- Add real-world scheduling scenario tests
- Ensure 100% line coverage for ProcessDetails class
- Follow project checkstyle rules and conventions

Fixes #6588

* fix: resolve SpotBugs UC_USELESS_OBJECT warning in ProcessDetailsTest

- Add assertions for process1 in testMultipleProcessesIndependence method
- Verify both processes are properly tested for independence
- Ensure all created objects are meaningfully used in tests

Fixes SpotBugs warning: UC_USELESS_OBJECT at line 224

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Co-authored-by: Oleksandr Klymenko <alexanderklmn@gmail.com>