WIP: Implement cond data and alg, and use cond data in SiDetElementsRoadMaker_xk (ATLASRECTS-4728)

Implement MagneticFieldCondData and MagneticFieldCondAlg, and use MagneticFieldCondData in SiDetElementsRoadMaker_xk via ReadCondDataHandle.

Drop IMagFieldAthenaSvc and callback from SiDetElementsRoadMaker_xk.

https://its.cern.ch/jira/browse/ATLASRECTS-4728

RunTier0Tests.py found tiny but many differences. I don't understand these differences. RunTier0Tests.log

Reco_tf.py --AMI q220
Reco_tf.py --AMI q221
Reco_tf.py --AMI q222
Reco_tf.py --AMI q223
Reco_tf.py --AMI q431
RunTier0Tests.py -o
athena.py --threads=1 --evtMax=10 --filesInput="/cvmfs/atlas-nightlies.cern.ch/repo/data/data-art/TrigP1Test/data17_13TeV.00327265.physics_EnhancedBias.merge.RAW._lb0100._SFO-1._0001.1" -c 'doCalo=False' TrigUpgradeTest/IDCalo.py

were OK.