Improved material surfaces outside of tracking region

[wdconinc]

These are all the plots material-map.tar.gz

Thanks. Can you remind me the reason to include structures that are way out of the tracking volume in this material mapping? We don't have any defined surfaces for material mapping there.

Because we want to propagate tracks to the front of ecals or to RICH detectors, and that requires the inclusion of material.

I see, in this case, the exit surfaces on backward MPGD or forward TOF disks can be used to collect materials up to the entrance of RICH. We need to add an ACTS surface between RICH and ECal to allow material being projected there. Materials by default will be projected onto the nearest available surface. With the current set up, the exit surface on the second negative MPGD disk is the last surface at backward direction, and it will get all materials from RICH, ECal, and beyond...

Originally posted by @ShujieL in #952 (comment)

[ShujieL]

example of creating representing surfaces for material mapping; acts-project/acts#2403