Add a simplified algorithm for computing the RICH detectable photon yields

Adds a new algorithm, AverageDetectablePhotonYields that uses average values for efficiencies such as the PD Q.E. values, mirror reflectivity's etc. to compute the detectable photon yield for each track.

The new algorithm is about 50 times faster than the full one (that makes an estimate track by track using the information associated to each track) such that using this new algorithm, this part of the RICH reco. sequence is no longer significant in terms of CPU usage.

With the current simulations this gives no change in PID sequence. I should note though that this is part is because the current simulations do not have different values for these quantities for different components. Once this changes in the simulation this should be checked again, however I suspect given how the detector yields are used, their importance in the PID algorithms, the use of average values compared to the full approach will likely not result in a significant PID drop even once we have a more complete detector description.

Note that the branch here is based off of !2007 (merged) so you will see the diffs here until that is merged.

Also note this MR will require new updates to the Brunel and Moore refs.

Requires LHCb!2487 (merged)