Use MessageSvc to handle ROOT messages

The default ROOT error handler (the equivalent of Gaudi MessageSvc) prints messages to stderr, which is problematic with Gaudi based workflows that expect all messages to go through stdout and be filtered according to MessageSvc output level.

This MR replaces the ROOT error handler with an adapter function that redirects to MessageSvc.

There are a couple of drawbacks which the changes proposed here:

• it works only if ROOT (gROOT) has been initialized before ApplicationMgr::configure, but my tests suggest this is always the case
• every message sent by ROOT makes a call to IMessageSvc::outputLevel( source ) to decide if the message has to be printed or not, while MsgStream instances cache the thresholds; we can optimize the adapter caching internally the thresholds (e.g. with a static std::unordered_map<std::string, int> thresholds) or by using a global threshold for ROOT messages.

GaudiExamples/tests/qmtest/refs/jira/gaudi_971.ref

@@ -59,7 +59,7 @@ EventSelector.D...  DEBUG Selection root:/Event CLID:110
 EventSelector        INFO Stream:EventSelector.DataStreamTool_1 Def:DATAFILE='LFN:input.dst'  SVC='Gaudi::RootEvtSelector' OPT='READ'
 ApplicationMgr       INFO Application Manager Initialized successfully
 ApplicationMgr       INFO Application Manager Started successfully
-TFile::TFile        ERROR file /builds/gaudi/Gaudi/GaudiExamples/tests/qmtest/none.dst does not exist
+TFile::TFile        ERROR file .../dummy.dst does not exist
 IODataManager       ERROR Error: connectDataIO> Cannot connect to database: PFN=dummy.dst FID=8BE41ECA-4004-11ED-8ECA-54AB3A714084
 IODataManager     WARNING Attempt to connect dsn:8BE41ECA-4004-11ED-8ECA-54AB3A714084 with next entry in data federation:ROOTIO.dst.
 FileRecordPersi...   INFO Added successfully Conversion service:RootCnvSvc