Aperture modelling tools for Xtrack

[szymonlopaciuk]

Description

First prototype of the aperture modelling functionality. See the examples for usage and the associated physics manual PR xsuite/xsuite#809.

Needs: xsuite/xobjects#169.

Currently allows:

• Loading an aperture model from a line with limits, a line with MAD-X metadata, or a line with associated_apertures defined on elements.
• Calculation of the n1 using different methods: by bisecting the beam envelope on the aperture polygon (bisection), using a linear-complexity approximated rays method, and a more precise quadratic-in-rays exact method.
• Calculation of the beam envelope at arbitrary sigmas and pipe cross sections.
• Can interpolate cross sections, even in curved, arbitrarily transformed types, with arbitrarily transformed profiles.

Caveats:

• GPU support not yet implemented.
• Interpolation along curved types uses an approximation (that should be "good enough" but should be kept in mind).

Checklist

Mandatory:

• I have added tests to cover my changes
• All the tests are passing, including my new ones
• I described my changes in this PR description

Optional:

• The code I wrote follows good style practices (see PEP 8 and PEP 20).
• I have updated the docs in relation to my changes, if applicable
• I have tested also GPU contexts