Add search summary panel

[jazairi]

Why these changes are being introduced:

It would be helpful if users could see what filters they've applied to a search directly below the search bar, which would also provide another path to remove filters.

Relevant ticket(s):

https://mitlibraries.atlassian.net/browse/GDT-142

How this addresses that need:

This provides the requested panel. We had been calling this a "filter removal" panel, but I ended up naming it "search summary" to avoid any confusion with the filter sidebar.

Side effects of this change:

The "You searched for" list has been removed, as this feature replaces it.

Developer

• All new ENV is documented in README
• All new ENV has been added to Heroku Pipeline, Staging and Prod
• ANDI or Wave has been run in accordance to
  our guide and
  all issues introduced by these changes have been resolved or opened as new
  issues (link to those issues in the Pull Request details above)
• Stakeholder approval has been confirmed (or is not needed)

Code Reviewer

• The commit message is clear and follows our guidelines
  (not just this pull request message)
• There are appropriate tests covering any new functionality
• The documentation has been updated or is unnecessary
• The changes have been verified
• New dependencies are appropriate or there were no changes

Requires database migrations?

NO

Includes new or updated dependencies?

NO

[jazairi]

Closing this for now, as I realized I missed a couple of details.