Add a toggle to remove personal collection results from search

**Is your feature request related to a problem? Please describe.**
An admin might be looking for a table in their database. However, there are many similar-named reports in various users' personal collections. This is especially a problem when there are many users in that instance.
In order to find the table the admin actually wants, they may have to scroll through several pages because the initial results are reports from personal collections.

**Describe the solution you'd like**
Having a toggle or some way to allow admins to hide reports from personal collections in search would be helpful in allowing admins to more easily find what they're looking for.

**How important is this feature to you?**
Would improve the admin experience

**Additional context**
Customer request

The issue names no files, entry points, or tests. Start by locating the search implementation and its coverage for personal collections, then determine how an admin-only toggle should affect results; done means admins can hide personal-collection reports and still find the intended table or report.

Written by the indexing model from the issue text.