Adding Phase-2L1Nano to central CMSSW

[artlbv]

I would like to start this issue to have a discussion about the (need of) adding the Phase-2 L1Nano to central CMSSW.
Input from our OFSW @epalencia @aloeliger and object contacts @EmyrClement @BenjaminRS @cerminar @folguera is appreciated!
FYI @slaurila @eyigitba

(Note that the P2GT decisions are already being monitored by the TriggerResults as the emulator uses an HLT-like setup)

Pros:

• Centralised location for the code / available in CMSSW directly
• We can have central test workflows for every PR (for now only comparing the size of the nano branches -> the number of objects/ev is already useful imho)

Cons:

• Tied to CMSSW releases etc -> less flexible or need dedicated branches e.g. in the L1 offline repo
• TPs (e.g. GTT) tables would need to be added to CMSSW (as was already before in their own ntuplers - really a con?)

Technical ingredients:

• P2GT decisions: use the P2GT PR (part) Phase-2 GT Step1 menu integration cms-sw/cmssw#44995
• L1nano: main repo https://github.com/cms-l1-dpg/Phase2-L1Nano/ includes L1 objects (GT inputs), GT objects and some TPs (for GTT)
• Idea to use autoNano: customise a la Phase-1, i.e. “L1DPG”: https://github.com/cms-sw/cmssw/blob/master/PhysicsTools/NanoAOD/python/autoNANO.py#L38-L40

E.g.

 'Ph2L1' : {'sequence': 'DPGAnalysis/Ph2L1Nano/l1tNano_cff.l1tNanoSequence',
               'customize': 'DPGAnalysis/L1TNanoAOD/l1tNano_cff.addFull, ...'},
'Ph2L1wTPs' : ..

Test workflows: could add a nano wf based on a ttbar file to produce ~100 nano events.