[MQ] slightly improve DigiEventSink by copying blocks of digis instead of looping through indices

- Add optional method to resort indicices to the CbmEvent class, as the indices for TRD1D and 2D are added in separate steps
- Replace the loop over the CbmEvent indices by a block copy between the first and last digi of each detector type, based
  on the assumption that we use a time-window based selection on a sorted array, therfore leading to a continuous block
  => this is known to potentially copy more digis in the TRD case due to the eventual =/= windows and offsets for 1D and 2D