Replacement of std::unordered_map in cbm::algo::tof::Calibrate.

@v.friese @f.uhlig @p.-a.loizeau @fweig @j.decuveland this might be of interest to you.

I made an attempt to make the TOF calibration faster, specifically the step where digis are discarded if they fail a deadtime check, by replacing the std::unordered_map which stores the channel addresses by flat vector, accessed by a unique index. At least theoretically, this should have eliminated expensive searches.

This appears to not change the runtime at all, at least on my machine. This leads me to conclude that the hash tables used by std::unordered_map are quite fast.

I don't intend to merge this, but wanted to report on this, for later reference. It might be useful in a different context.

Edit: Might be worth merging, see below.