Make all necessary fixes to fully run Example 3
This MR focuses on Example 3, where we need to change:
- Many of the Example 3 configs, which were out-of-date with the updates to the rest of the library
- A couple of minor refactors in the data reading, to allow for data without cluster features, and to add "hardware" key to TrackML data
- Enforced pT to be in MeV, to make consistency between ITk and TrackML pipelines
- Updated Example 3 README to be more clear about how to use the optional filtering stage
NB - I tested the updated DataReader with the other examples, and it's fine
Edited by Daniel Thomas Murnane