ACTS KF: Switch to `SympyStepper`
Similar to what we did for the ACTS CKF we can make use of the SympyStepper
for the KF to improve CPU performance.
GitLab jobs artifacts no longer stored forever as of Monday, November 4th 08:30h. Further information under https://cern.ch/otg0152576
Similar to what we did for the ACTS CKF we can make use of the SympyStepper
for the KF to improve CPU performance.