CbmAlgoBuildRawEvents: Set histogram axes to adaptive + remove last access to FairRootManager

The 2019 event builder contained some histograms with fixed axis ranges, which are related to the length of time slices. In the present commit, the axes were changed to the adaptive mode, to automatically adjust to different time slice lengths. Also removed some unused class-wide variables and moved read operation of time slice meta data array from FairRootManager from Algo to Task.

Suggested reviewer: @p.-a.loizeau