Add a URI field in Visual Metrics Editor

[medriscoll]

When editing a dimension's properties in the Visual Metrics Editor I would like to be able to toggle whether the dimension contains an attribute of a clickable URI.

This field can be at the bottom of the right-side panel, with a heading 'URI' and three options of "None", "Literal", and "Expression".

None is the default selection.

Choosing literal will populate uri=true.

Choosing Expression will reveal a text box where an arbitrary SQL expression can be created.

https://docs.rilldata.com/build/dashboards/#clickable-dimension-links

[medriscoll]

@jkhwu Feel free to comment on design here, this is my suggested path but I'm happy to defer to anything you and Brian agree on (I'm just firing these into our public Github repo but I recognize we may want to do a design pass on these).