Adapt to IBS Convention Changes

[fsoubelet]

Description

This is the first of 3 sibling pull requests enacting the change in IBS convention to return amplitude growth rates for consistency with synchrotron radiation damping times, instead of the current emittance growth rates.

It is explicitely stated that IBS growth rates are in amplitude convention in the xtrack.TwissTable API. The particles parameter has been removed like in xfields.

There is also an API relay addition for a future xfields PR to be opened after the convention change, as well as a lattice file addition for the same future PR.

Should be merged as the first of the three, as it is needed by xsuite/xfields#163.

Checklist

Mandatory:

• I have added tests to cover my changes (yes, in xfields PR)
• 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