Make sure there is a TGeoNavigator per thread before calling Contains

Required to make FTHitEfficiencyMonitor work when multi-threaded, as currently the geometry navigation is not configured for multi-threading.

Requires LHCb!4652 (merged) where the number of threads is set.

I provided a detailed description of the relevant functions in LHCb!4652 (merged), and then on slide 8 (titled "Usage") of this very old presentation describing the parallelisation of the ROOT Geometry library (the only relevant documentation I could find) it shows the required change in this MR https://indico.cern.ch/event/193979/contributions/357987/attachments/280434/392148/ParallelizingROOTgeometry.pdf

I think this is the correct ROOT way to do it, but in future we can probably find a better way to do it.

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Validated by

• Core Software
• RTA
• Simulation