Summary

Adds validation to prevent cvars and uvars from using names that would shadow built-in functions.

Changelog Entry

• Cvars and uvars can no longer shadow built-in function names

Checklist

PR Type

• This PR is a code change that implements a feature request.
• This PR fixes an issue.
• This PR adds a new feature that is not an open feature request.
• This PR is not a code change (e.g. documentation, README, ...)

Other

• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• If code changes were made then they have been tested.
• I have updated the documentation to reflect the changes.