issues with reduced diagnostics and their post-processing tools

[aeriforme]

This issue relates to PR #3752 for the development of post-processing tools of reduced diagnostics.

A list of open issues to address follows (and more to be found):

• RZ geometry (e.g. missing FieldProbe)
• boosted frame
• possibly standardize names of the diagnostics leaving the option of appending an arbitrary string
• the units in some diagnostics are wrong in non-3D geometry (e.g. RhoMaximum)
• missing readers:
  • FieldProbe
  • FieldReduction
  • BeamRelevant
  • ParticleHistogram
  • LoadBalanceCosts
  • LoadBalanceEfficiency
  • ChargeOnEB
• integrate the tools in the python workflow
• consider how to maintain the tools in case of new future diagnostics or future modifications to the existing ones

@ax3l @roelof-groenewald @dpgrote @camille12225

[Yin-YinjianZhao]

Recently I also encountered a missing feature, which is that the FieldProbe reduced diagnostic does not support RZ yet.
Hope this is not a lot of work and someone can spend some time working on this soon.
Thanks!