Reduce the number of files in MG gridpacks
As discussed in ATLMCPROD-8537, there are a large number of files in the LO MadGraph gridpacks that we are currently keeping but don't actually need. This MR removes them, keeping only the integration grids and the results.dat
.
For NLO gridpacks, also remove the events.lhe
and optional events.lhe.rwgt
files created for the original gridpack run.