* Add PHP type hints where possible.
* Remove @var, @param and @return if redundant to type declaration
* Remove redundant type conversions which are now enforced by type
hints.
* Enforce that decodeBoolean returns only a bool.
Change-Id: I8da84ed4dc778dd9d84f8d9eec0a399f5ed26405
Replace the dynamic property on SpecialTrackingCategories object,
this was used to store preloaded Category objects.
Dynamic properties are deprecated in php8.2
The preload and storage is now done with the service.
Adjust doc to LinkTarget (Id0cc2ca)
Bug: T324897
Change-Id: I891ad79bc357d32585ef4d9206d398c5a75222aa