Change distribution default parameters to Twiss in dashboard

[proy30]

This PR updates the primary option for beam distribution configurations to "Twiss". The previously primary set, "Native," has been renamed to "Quadratic Form" and is now available as an alternative parameterization for users.

In addition, this PR makes minor adjustments to the code structure and docstrings within the beam distribution section. These changes do not affect functionality.

Tested with this example to ensure correct functionality.

Checklist

• [X] Set "Twiss" as the default, with "Quadratic Form" as the alternative option.
• [X] Update dashboard functionality to correctly display twiss and to read through simulation
• [X] Update export templates to correctly handle the "Twiss" parameterization.
• [X] Ensure the "Thermal" distribution uses only a single set of parameters.

I noticed that all beta/emitt parameters must have non-zero values, but this validation is missing in the current PR. PR #690 includes a modified helper function with built-in validation capabilities for non-zero values. Better to either include beta/emitt validation in that PR or in a new one once #690 is merged.

Resolves #724

[proy30]

Tested inputs from https://impactx.readthedocs.io/en/latest/usage/examples/distgen/README.html#a-6d-gaussian-distribution-from-twiss-functions Output

[EZoni]

As far as the AppleClang CI check is concerned, we probably need to rebase after #750 is merged.

[proy30]

Updated with units