CuPy pre-release or nightly testing

[jakirkham]

RAPIDS depends heavily on CuPy and does tests stable versions of CuPy when developing RAPIDS.

However there is currently limited testing of CuPy with RAPIDS during development. As a result, sometimes issues can crop up after a CuPy release that were not caught earlier.

Currently this is what exists:

• CuPy tests narrow portions of stable RAPIDS used by CuPy ( originally introduced in PR: Add CI for pylibcugraph cupy/cupy#5874 )
• Specifically cuML tests with pre-release CuPy wheels ( originally introduced in PR: CI: Test CuPy nightlies cuml#7695 )

To help prevent this, RAPIDS should adopt broader testing of CuPy nightlies or pre-releases. As cuML started this with pre-releases, this could provide a good initial template to build out more RAPIDS testing of CuPy pre-releases.

For CuPy nightlies testing, we would need nightly binaries from CuPy, which don't exist yet. This tracked in issue: cupy/cupy#9974

By doing this RAPIDS should be able to report upstream issues with CuPy during development before releases to ensure fewer issues show up after CuPy releases.

[jameslamb]

Let's keep an eye on this: scientific-python/upload-nightly-action#169