External Pythia8+Powheg generator

[jackal1-66]

The generator has been tested using both o2-sim and the normal workflow system.
Nothing to report with normal o2-sim, however for the workflow system I noticed that it's not possible
to configure properly the parameters in the funcName => There might be a small bug that doesn't allow " to be used or that discards it. With the workflow framework both the configuration via iniFile and hybrid JSON worked flawlessly.

[github-actions]

REQUEST FOR PRODUCTION RELEASES:
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The following labels are available
async-2023-pbpb-apass4
async-2023-pp-apass4
async-2024-pp-apass1
async-2022-pp-apass7
async-2024-pp-cpass0
async-2024-PbPb-apass1
async-2024-ppRef-apass1

[vkucera]

Thanks a lot @jackal1-66 !

[jackal1-66]

The CI failing is fixed by alisw/alidist#5745, waiting for the merging to retest

[jackal1-66]

All CI tests passing, can be merged