Unit tests PPA (EXPOSUREAPP-6723) (#3313)

* add storage

* adjust donor

* refactor detector

* tests

* fix tests

* fix tests

* klint

* fixes

* fix crash

* fix shared prefs

* fix shared prefs

* detekt

* refactoring

* fix tests

* fix type
klint

* remove unnecessary storage

* use last calculated

* remove change detector

* use last calculated

* fix test

* merge 2.4

* fix naming

* fix getLastChangeToHighRiskPt/Ew

* calculations unit tests

* refactoring

* refactoring

* merge 2.4

* more tests

* rename

* detekt

* merge 2.4

* fix order

Co-authored-by: Mohamed Metwalli <mohamed.metwalli@sap.com>