Improve Activity Subject/Details text search to be similiar to Notes Subject/Body

Let's improve for CiviCRM core the way the text search works for Activities. Other than the name being slightly different "subject/details" vs. "subject/body", Activities text search could work the same as Notes.

Note that any text string such as "meeting" or "dog" could be searched, and as seen in the attached, the toggle for Subject, Body/Details, or both.