Simplify details for utility completions

[thecrypticace]

Fixes #1347

This PR addresses two problems (see screenshots below):

1. Utilities that generate @property rules will include the declarations from @property in the completion details.
2. Custom variants that include declarations will include those declarations in the completion details.

To fix these we are now:

1. Generating details using the "base" utility
2. Dropping any uses of @property before calculating the list of declarations

Before

After

Note that the "documentation" portion of completion items is unchanged and shows the full candidate with all the CSS included (for non-color utilities):