ISF_FastCaloSimEvent: replace MsgStreamMember with MsgStream
This MR reverts the changes to TFCSParametrizationBase done in !53224 (merged) and replaces the use of MsgStreamMember with a plain MsgStream. This is obviously not thread-safe and would require further work. Using AthMessaging is not an option in this case as
TFCSParametrizationBase needs to be ROOT-storable.
Relates to ATLASSIM-5854.
Edited by Frank Winklmeier