Add option to filter search results with only custom variables or default variables

[#1]

This idea was on the old forum, but after the migration I couldn't find it anymore so I wrote a new one. Curation and variable settings in virtual report suites have helped a lot when we want to adjust variables for certain project etc. However, the basic search in Workspace could need some adjustments and then it would be easier and faster to find right variables (especially for new users).

I can think of many kinds of filterings that would be a big help, but filtering by custom variables (or by default dimensions) is one of the most wanted wish for the search.

I have few other ideas written separately for the search.

I guess this is easy to understand. There could be some kind of link/button/icon to get search results only for custom variables (props,eVars,events) or option to see

only default / out of the box dimensions and metrics.