AthenaKernel, etc: Additional DataBucketBase::cast overload.

There have been two overloads for DataBucketBase::cast, one taking a clid and one taking a type_info. To cast from a DataProxy, we've been using the type_info version. However, doing it with a clid can be a bit faster, so we'd like to use that. There is a problem, though, since xAODRootAccess also implements a DataBucket, but this version only supports casting via type_info.

So add a third overload for cast that takes both a clid and a type_info and give the callee the opportunity to choose which one to use.

Update appropriately classes derived from DataBucketBase.