JetMonitoring EventHistoVarTool: Add eventinfo attribute dependency to avoid scheduling issues (ATR-27392)

Purpose

• Adding ReadDecorHandle for EventHistoVarTool for EventInfo decoration used by tool. This makes decoration an explicit dependence of tool, which sorts out proper algorithm scheduling.
  • Made it so that one can explicitly set event info container name, like EventHistoVarTool.Attribute = myEventInfo.myAttribute. But by default and the way the python code is configured now, "EventInfo" is assumed and prefixed for the decoration retrieval so that no python code changes necessary.
• Addition of ReadDecorHandle made it unnecessary to pass in EventInfo container as argument in EventHistoVarTool getter function. Ignoring EventInfo argument for JetEventSelector incarnation of IJetEventSelector, as this uses configured EventHistoVarTool.

Effects

• Changes offline/Tier0 HLT jet monitoring distributions that select on "averageInteractionsPerCrossings" - "lowmu" and "highmu" distributions. These are now properly filled.
• No other changes expected, as this package only used by jet trigger group for offline monitoring.

Notes

Technically, in previous code one could have passed in an xAOD::EventInfo container with different key by explicitly configuring this for the parent jet monitoring alg (which uses a tool that uses this tool) - at moment, default "EventInfo" is used. It seemed like some work to modify python config or c++ code to pass this down. Hence, instead here made it possible to configure the full container+decoration via the "Attribute" property of EventHistoVarTool tool.