rapids-cmake support empty patches array in json

[robertmaynard]

Description

This allows overrides to explicitly opt-out of the patches that rapids-cmake lists in the built-in versions.json Previously you would get a rapids-cmake parsing error when trying to do this.

Checklist

• [x] I am familiar with the Contributing Guidelines.
• [x] New or existing tests cover these changes.
• [x] The documentation is up to date with these changes.

[robertmaynard]

/merge