[RELEASE] dask-cuda v23.12

[raydouglass]

❄️ Code freeze for branch-23.12 and v23.12 release

What does this mean?

Only critical/hotfix level issues should be merged into branch-23.12 until release (merging of this PR).

What is the purpose of this PR?

• Update documentation
• Allow testing for the new release
• Enable a means to merge branch-23.12 into main for the release

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