[Dashboard] Distributions via Twiss

[ax3l]

Let's change all the distribution input to only accept CS/Twiss parameters.

Example:

• https://impactx.readthedocs.io/en/latest/usage/examples/distgen/README.html#a-6d-gaussian-distribution-from-twiss-functions
• https://github.com/ECP-WarpX/impactx/blob/development/src/python/impactx/distribution_input_helpers.py#L12-L25

I propose to fully replace the lambda=.. input and only support the twiss parameters. To discuss with @cemitch99 and @n01r

[n01r]

I would be in favor. :+1: I still like offering helper functions that transform other common inputs to our input conventions but I am for moving towards CS/Twiss parameters as the new default.

[ax3l]

Yes, and for the dashboard I would only offer CS/Twiss for now, no alternatives.