Tangent vector application in track seeding

• Neural network can predict tangent vector to track trajectory -> This can be used in seeding
• Network predicts sector-local dy/dx and dz/dx => In neighbour finding we can use e.g. y + NN_dydx*dx

Implemented. Draft-PR for discussion: https://github.com/AliceO2Group/AliceO2/pull/15582

So far reproducing the same number of tracks within 0.5‰. Slow-down due to additional computations: 2.93±0.01 s/TF (NN class + reg, epn000) -> 3.15±0.013 s/TF (NN class + reg + mom vector, epn000). (Default reco is 2.06±0.01 s/TF)

Need to do MC investigation now.

LHCP proceedings: https://alice-conferences.web.cern.ch/node/70501

CHEP proceedings: https://alice-conferences.web.cern.ch/node/70535

ICHEP slides: In preparation