Draft: [mCBM] Digi filter around spill start in legacy unpacker

See commits

Draft mode until following fixed

• Hard-coded path to accelerator event files (probably enough if hardcoded to somewhere in production) => Changed to point the final location on lustre
• Options values: filter window limits, ...
  => Need setters
• Testing by main detector users (STS, TRD, MUCH, ...) + effect on event building & tracking
  => Will probably never happen, but changes not expected to interfere with original mode of operation