add Acts CKF branch stopper for maxHoles

Tim Adyerequested to merge
adye/athena:adye-ckf37 into main

Currently only Acts::CombinatorialKalmanFilterTipState is available to the BranchStopper, which allows us to stop on nHoles. This can be varied in bins of |η| from the seed.

Acts Core PR #2714 will add TrackStateProxy, allowing additional tests and using |η| from the track state.

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