Xfields

**Changes:**
- Introduce `z_kick_num_integ_per_sigma` in `xf.SpaceChargeBiGaussian`.
- Implement `apply_z_kick` in `SpaceCharge3D`.
- Introduce `LongitudinalProfileQGaussian_line_density_derivative_scalar`

**Full Changelog**: https://github.com/xsuite/xfields/compare/v0.17.0...v0.18.0

**Changes:**
- Introduce `IBSKineticKick` and `IBSAnalyticalKick`.

**Full Changelog**: https://github.com/xsuite/xfields/compare/v0.16.0...v0.17.0

**Changes:**
- Add computation of IBS growth rates.
- Reorganize beam beam 3d code.

**Full Changelog**: https://github.com/xsuite/xfields/compare/v0.15.1...v0.16.0

**Changes:**
- Adapt to new Xtrack behavior on json load
- Faster beam-beam element insertion

**Full Changelog**: https://github.com/xsuite/xfields/compare/v0.15.0...v0.15.1

**Changes:**
- Introduce `FFTSolver2p5DAveraged`
- In space charge config tool keep the line buffer and get particle_ref from line when possible.
- Switch to fast element insertion in spacecharge tools.

**Full Changelog**: https://github.com/xsuite/xfields/compare/v0.14.2...v0.15.0

**Changes:**
- Prepare for `FFTSolver2p5DAveraged` implementation.

**Full Changelog**: https://github.com/xsuite/xfields/compare/v0.14.1...v0.14.2