Add pion+ track reconstruction benchmark

benchmarks/tracking/central_pions.sh

benchmarks/tracking/config.yml

benchmarks/tracking/run_tracking_benchmarks.py

benchmarks/tracking/scripts/gen_central_pions.cxx

benchmarks/tracking/scripts/hits_central_pions.cxx

benchmarks/tracking/scripts/rec_central_electrons.cxx

benchmarks/tracking/scripts/rec_central_pions.cxx

benchmarks/tracking/scripts/tracking_performance.py