ZDC development branch to be merged into 21.2

There was a mistake happened during the last MR. So a new MR is required and references to the old one: !35437 (merged)

Update info from previous MR:

1. Updates to pulse fitting to improve performance for 2018 PbPb
2. Add repass for the pulse fitting to reduce the effect of the low energy peak (lower than 1n peak) which is due to the large pile-up events.
3. Improve the baseline matching performance for delayed and undelayed samples.
4. Change the 2018 fit function to "FermiExpLinear".
5. Update standalone test files in "tools" folder.