ATR-19303: Example to configure simple example electron chain

ElectronDef.py and generateElectronChainDefs.py are now in a state such that a simple electron chain can be configured. Tagging @tbold and @fpastore

To be addressed in a different MR:

• MenuChains.py: remove the hardcoded dict for hypo tool configuration
• Noticed that chains have to be named with HLT_ prefix due to Trigger/TrigHypothesis/TrigEgammaHypo/python/TrigL2ElectronHypoTool.py (TrigL2ElectronHypoToolFromName), once this is changed, can work with just chain name without HLT_ prefix

Note:

• ElectronDef.py might need further tidying up (in terms of removing getStep, getFastCaloStep or getElectronStep) but since in dev, will keep it for now as the code might become more complex as well, so these functions might be needed. Might need to consider designing a base class with some functions that can be shared across signatures.