Descheduler code refactorings

[ingvagabund]

Refactoring the code to improve readability and maintainability by simplifying logic, clarifying names, organizing structure, and ensuring consistent style—without changing existing functionality.

TestPodLifeTime:

• refactor(TestPodLifeTime): remove ineffective owner references assignments #1781
• refactor(TestPodLifeTime): have a pod fully created through BuildTestPod without any edits #1782
• refactor(TestPodLifeTime): consolidations, simplifications and node instance for each unit test #1783
• refactor(TestPodLifeTime): inline pod creation in each unit test to avoid accidental pod spec updates #1784
• refactor(TestPodLifeTime): update unit test names and simplify pod creation #1785
• feat(TestPodLifeTime): check only expected pods are evicted #1787
• feat(PodLifeTime): document the plugin with details that can be used for reasoning during reviews and design discussions #1789
• refactor(TestPodLifeTime): split the unit tests into smaller semantically close groups #1790

TestFindDuplicatePods:

• refactor(TestFindDuplicatePods): have a pod fully created through BuildTestPod without any edits #1791
• refactor(TestFindDuplicatePods): reduce duplicates and inline #1792
• refactor(TestRemoveDuplicates): reduce test code duplication #1793