Change search widget toggle behavior

[hanzala-sohrab]

This PR is related to the issue #952.

Changes made in this PR:

• Pressing Ctrl F will enable search widget.
• Pressing Ctrl F again will not toggle off the search widget. Instead, the search widget will be refocused.
• The search widget can be toggled off by pressing Escape key.

[hanzala-sohrab]

@diegogangl Can you verify these changes?

[nekohayo]

This needs to be rebased to the latest master. Apologies for the inconvenience.

At the same time, it is a duplicate of @sladkkr's #964, so you two might want to coordinate on this.