[IMPROVEMENT] User: Improve PHP types in User/Profile

[mjansenDatabay]

This PR improves the type documentation in the
Profile sub-namespace of the "User" component.

Other (relevant) Changes:

• throw \InvalidArgumentException('This user does not exist.'); (new operator missing)
• In DatabaseDataRepository::deleteForFieldIdentifier we called manipulateF instead of manipulate
• CachedConfigurationRepository::buildCustomFieldDefinitions expected a wrong return type from array_search (which will return false and not null in case a value could not be found)

If approved. please pick to trunk as well.