Close current filter dropdown by pressing Esc button

Description

While filtering, a small popup appears to allow the user to select fields such as Assignee, Author, etc. to be filtered on. This automatically pops up as soon as I have focus in the filter bar box. There are three parts to the filter, the field, the operator, and the search value. All three of these fields respond to escape differently. In this issue, it is proposed that if escape is pressed when the field is selected, then the field popup closes.

This happens on the filter bars for issues/mr/epics. Added a newer image to reflect the latest appearance.