Hide tooltip instantly on filter change

Summary:
Instantly hide tooltip shown over an element when filter bar changes.

Currently the tooltip stays even when filtering causes the file under the mouse to change or disappears entirely.
The tooltip also continues to cover much of the window - hiding the new filtering results from user.

This is an enhancement to D22512

Test Plan:
1. place the mouse pointer over a file to show the tooltip
2. press "/" to activate filter bar
3. type in filter phrase

Reviewers: #dolphin, elvisangelaccio, ngraham

Subscribers: kfm-devel

Tags: #dolphin

Differential Revision: https://phabricator.kde.org/D26576