Xobjects

**Changes:**

- Bugfix: when return value of Method is None, don't return anything (freddieknets in https://github.com/xsuite/xobjects/pull/141)


**Full Changelog**: https://github.com/xsuite/xobjects/compare/v0.4.4...v0.4.5

**Changes:**
- Use weakset to keep track of allocated buffers.
- Copy of LinkedArray is now a native array

**Full Changelog**: https://github.com/xsuite/xobjects/compare/v0.4.3...v0.4.4

**Changes:**

- Build OpenCL kernels with CL2.0 (needed for __generic args)
- Bugfix: select correct devices when tests run with `XOBJECTS_TEST_CONTEXTS`

**Full Changelog**: https://github.com/xsuite/xobjects/compare/v0.4.2...v0.4.3

**Changes:**
- Add `np.squeeze` in `xobjects.assert_allclose(...)`

**Full Changelog**: https://github.com/xsuite/xobjects/compare/v0.4.1...v0.4.2

**Changes:**

* Move assert_allclose to general to avoid a hard dependency on pytest by szymonlopaciuk in https://github.com/xsuite/xobjects/pull/133


**Full Changelog**: https://github.com/xsuite/xobjects/compare/v0.4.0...v0.4.1

**Changes:**
- More compact json files (avoid saving parameters equal to the default)
- Introduce `HybridClass._force_moveable` flag.
- Introduce `assert_allclose` capability to facilitate tests.

**Full Changelog**: https://github.com/xsuite/xobjects/compare/v0.3.1...v0.4.0