PR validation on pileup sample doesn't seem to use overlay collection in tracker dqm

[bryngemark]

Describe the bug
I was checking the validation histograms from iss #1699 and e.g. the recoil track multiplicity closely resembles the distribution in the ecal PN validation suite.

To Reproduce
Steps to reproduce the behavior:

1. Go to Add CLUE clustering #1699
2. Click on the validation checks --> view details --> Summary
3. Scroll down to Artifacts
4. Download it_pileup and ecal_pn plots, and compare the Ntracks distribution in the recoil tracker (examples added here)

Desired behavior
The validation suite on pileup uses pileup collection input everywhere.

Plots
from ecalPN+pileup run
RecoilDQM_RecoilDQM_N_tracks.pdf
from 1e ecal PN run
RecoilDQM_RecoilDQM_N_tracks.pdf