Optimize TRT validity gate for run2 data.

To suppress out-of-time pile-up, TRT RIOs are required to pass the low level threshold within a certain time window, the validity gate (VG). This MR implements a new tuning of the VG using a sample of 2018 data, separately for Xe and Ar hits. As a result, the number of precision hits on track increases by about 1.5%, while the total size of the RIO container (the Argon part of it, that is) shrinks by about 1%.