Xobjects

**Changes:**
- Allow overriding of hybrid classes in kernel compilation.
- Add a new field `_cname` which allows to manually specify the name of the generated XoStruct.
- Change `context.sort_classes` such that duplicated classes appearing later in the list override the ones that appear earlier.
- Associate kernels in their contexts not only with their name but also the overridable classes that they were built with.

**Full Changelog**: https://github.com/xsuite/xobjects/compare/v0.1.32...v0.2.0

**Changes:**
- Patch `pyopencl` module with mean, sqrt and isnan.
- Add some more scalar types to GPU contexts

**Changes:**
- Introduce compile_kernels method in all contexts.
- On ContextCpu, kernels can be saved or loaded from shared-object files.

**Full Changelog**: https://github.com/xsuite/xobjects/compare/v0.1.30...v0.1.31

**Changes:**

- Minor linting

**Full Changelog**: https://github.com/xsuite/xobjects/compare/v0.1.28..v0.1.30

**Changes:**

- Implement `to_nparray` and `to_json` and add suitable tests for xobjects. The method `to_json` returns a dict that is json-compliant from which the xobjects can be regenerated simply by passing the dict to the constructor.
- Avoid memcopy (where possible) in a hybrid class.
- Make contexts visible in test printout. Parametrize tests over contexts simply by adding `for_all_test_contexts` or `for_all_test_contexts(excluding: Iterable[str] | str)` on them, the context is passed as `test_context` to the test.
- Minor fixes of typos.

**Full Changelog**: https://github.com/xsuite/xobjects/compare/v0.1.27...v0.1.28

**Changes:**
- Add _update method to class to avoid overwriting arrays.
- Ensure that NULL is defined in pyopencl contexts.

**Full Changelog**: https://github.com/xsuite/xobjects/compare/v0.1.26...v0.1.27