Sparseconverter

* Better error message in case of unknown array type: https://github.com/LiberTEM/sparseconverter/pull/37
* Support for SciPy sparse arrays: https://github.com/LiberTEM/sparseconverter/pull/52
* Drop support for Python 3.7: https://github.com/LiberTEM/sparseconverter/pull/51

* Support for Python 3.12 https://github.com/LiberTEM/sparseconverter/pull/26
* Packaging update: Tests for conda-forge https://github.com/LiberTEM/sparseconverter/pull/27

* Perform feature checks lazily https://github.com/LiberTEM/sparseconverter/issues/15

* Detection and workaround for https://github.com/pydata/sparse/issues/602.
* Detection and workaround for https://github.com/cupy/cupy/issues/7713.

Include version constraint for `sparse`.

Adds the following features:
* Introduce `conversion_cost()` to obtain a value roughly proportional to the conversion cost
between two backends.