Draft: search: Add search deamon and example app using it

This is on top of !1077 (closed) to implement the remaining TODO tasks.

TODO (From !1077 (closed))

• PhoshSearchResultFrame: implement item_activated
• allow tools/search to display search results
• and tools/search-view to display search results using the UI widgets
• allow tools/app-grid to use searchd to display search results via PhoshSearchResultFrames
• same for phosh's overview
• update doc comments from old gtk-doc format

Special thanks to Rudra Pratap Singh for his code contribution.

Demo Video

demo

Fixes: #410