Move TrigT2BeamSpot from FexAlgo to AthReentrantAlgorithm. Removes Run 2 operation

Stewart Martin-Haughrequested to merge
smh/athena:beamspot_to_AthReentrantAlgo into master

Make T2VertexBeamSpot an AthReentrantAlgorithm. Can no longer run in Run 2 mode - part of ATR-22712.

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