Non-fiducial DM search

[tvami]

Issue description

Tasks

• Create bkg simulations
• Find the cuts that categorize this to be non-fiducial, start with the ecal veto's non fiducial variable
• Train a specific BDT for non-fid bkg vs non-fid signal
• Maybe train PNet to do the same Non-fiducial ECal ParticleNet Study #35

Existing material to start off

• Old Config: https://github.com/LDMX-Software/ldmx-sw/blob/trunk/Biasing/test/ecal_pn_nonfiducial.py
• Source 1