Add workflow to update gpuCI

[charlesbluca]

Adds a workflow similar to dask-docker's Dask updating workflow to update the RAPIDS_VER used by gpuCI when a new nightly version of cuDF is available.

• Closes #xxxx
• Tests added / passed
• Passes black dask / flake8 dask / isort dask

[charlesbluca]

Is there an easier way to do this? Essentially the output of the above action will be something like 21.12.00a211004 and we want to strip the tags so that it's just 21.12. To my knowledge, GHA doesn't let you do string manipulation for env variables, so we can't do something like:

${{ steps.latest_version.outputs.version[:-10] }}

[charlesbluca]

Any suggestions on labels / reviewers? Would probably make sense to add some maintainers that are members of RAPIDS

[jrbourbeau]

We can probably leave off labels for now. For reviewers, I'll suggest dask/gpu instead of specific individuals. This will ensure folks from RAPIDS are pinged.

[charlesbluca]

That makes sense, though it looks like we might need to use a non-default GitHub token when opening the PR in order to request review from a team:

peter-evans/create-pull-request#155 (comment)

[jrbourbeau]

Thanks @charlesbluca! Having this automatically handled will be nice

cc @jacobtomlinson

[jacobtomlinson]

This looks great. Sadly the string manipulation step is necessary.

I guess we should get this merged and see how it performs.

[charlesbluca]

Thanks @jacobtomlinson - yeah, I think it makes sense to try the workflow out in this repo for the next release cycle and depending on how that goes, adding an updated (or identical) version of this to Distributed.

[jacobtomlinson]

Test failures are unrelated. Merging.