Remove & Retention: Replace "fake" unit tests with real ones along refactoring the production code to make it testable

[buhtz]

Describe the problem, feature or ask a question:

Currently the existing "unit tests" related to Remove & Retention are "fake" because they do not test the productive code but code surrogates.

The task are, to refactoring the productive code to make it testable.
Adapt the existing unit tests to the productive code.

Meta issue:

• Revise Auto- and Smart-Remove feature #1945

[buhtz]

Seems to me like "AI" generated text. If you are to lazy, approaching this project with self written text, I am to lazy reading your text. I am also reporting you to Microsoft GitHub abuse team in hope they will ban you and you won't bother other FOSS projects anymore and burn their resources.