dRICH: propagate tracks to spherical mirrors

**Is your feature request related to a problem? Please describe.**
Besides knowing the propagated `TrackPoint`s in the vessel, it would be very useful to know the position and direction of the track as it passes through the dRICH mirror. Then one could analytically determine where the track would hit the dRICH sensors, if it were to reflect off the mirror. Ignore B-field after reflection, since our goal is to know roughly where to expect the Cherenkov photons, in order to assist PID algorithms to know what fiducial volume to check.

**Describe the solution you'd like**
- Generate ACTS spherical surface, for our mirrors
- Add collection `DRICHMirrorTracks`: these are `TrackSegments` with one `TrackPoint` on the mirror; can be produced by `RichTracks_factory`

Start by reading RichTracks_factory and the existing TrackPoint and TrackSegment handling. Review how ACTS surfaces are represented in the reconstruction code, then trace the vessel track propagation path. Done means spherical mirror surfaces are represented and a DRICHMirrorTracks collection contains the requested mirror track points and directions.

Written by the indexing model from the issue text.