* aoc/am: Cleanup aoc service and stub am calls
This PR implement aoc call `GetAddOnContentListChangedEventWithProcessId` (Closes#2408) and `CreateContentsServiceManager`. Additionnally, a big cleanup (checked by RE on latest firmware) is made on the whole service. I've added `CountAddOnContent`, `ListAddOnContent` and `GetAddonContentBaseId` for games which require version `1.0.0-6.2.0` too.
Am service call `ReportUserIsActive` is stubbed (checked by RE, closes#2413).
Since some logic in the service (aoc) which handle the DLCs has been changed, it could be nice to have some testing to be sure there is no regression.
* Remove wrong check
* Addresses gdkchan feedback
* Fix GetAddOnContentLostErrorCode
* fix null pid in services
* Add missing comment
* remove leftover comment
