Xfields

**Changes:**
- Fix in `ElementWithSlicer`

**Full Changelog**: https://github.com/xsuite/xfields/compare/v0.21.1...v0.21.2

**Changes:**

- Fix strongstrong slice moment bug by swapping sign of `px_slice_star` and `py_slice` star in `beambeam3d.h`, clean up `bhabha_spectrum.h` (146)

**Full Changelog**: https://github.com/xsuite/xfields/compare/v0.21.0...v0.21.1

**Changes:**
- Introduce `BeamBeamPIC3D` element

**Full Changelog**: https://github.com/xsuite/xfields/compare/v0.20.3...v0.21.0

**Changes:**
- Preparing for deployment of Wakefields in Xwakes

**Full Changelog**: https://github.com/xsuite/xfields/compare/v0.20.2...v0.20.3

What's Changed
* Fix issues with spacecharge on OpenCL after Numpy 2 release (https://github.com/xsuite/xfields/pull/132)


**Full Changelog**: https://github.com/xsuite/xfields/compare/v0.20.1...v0.20.2

**Changes:**
- Introduce slicer cability
- Introduce Wakefields (still experimental)
- Introduce Transverse Damper (still experimental)
- Introduce `install_spacecharge_frozen(..., z_kick_num_integ_per_sigma=...)`
- Fixes in IBS GPU tests.

**Full Changelog**: https://github.com/xsuite/xfields/compare/v0.18.0...v0.20.0