Add dispersion to reduced diagnostics

[cemitch99]

trafficstars

Modified the reduced beam diagnostics to include beam-based dispersion values dispersion_x , dispersion_y and their derivatives dispersion_px, dispersion_py. Close #678.

The transverse Twiss functions beta_x, beta_y, alpha_x, alpha_y were modified to account for correlations with energy in a dispersive beamline.

• [x] Add horizontal dispersion and modify horizontal Twiss calculations
• [x] Add vertical dispersion and modify vertical Twiss calculations
• [x] Modify output of reduced diagnostics to include dispersion
• [x] Add benchmark test
• [x] Add read of reduced diagnostics to analysis script
• [x] Modify documentation

[cemitch99]

ImpactX_MADX_Twiss_Dogleg_Comparison.pdf

[cemitch99]

All tests currently pass except Windows. Windows test fails because of trouble opening diags/reduced_beam_characteristics_final.0.0

[ax3l]

Note: Windows / MSVC w/o MPI shared currently fails #650 but in a later test.

[ax3l]

@cemitch99 oh, we forgot to update the documentation in https://impactx.readthedocs.io/en/latest/dataanalysis/dataanalysis.html#reduced-beam-characteristics

[ax3l]

Added in #686