IOVDbFolder: introduced new private function fetchCrestObjects()
As the name suggests, this function contains code that retrieves data from
the CREST database and stores it in the objects of type BasicFolder
.
The changes in this MR are mostly moving the existing code around in preparation for adding support for reading multiple IOVs from the CREST database in a single Athena job. Also, there are a few shortcuts/temporary solutions that are expected to be reworked in the next MR-s