Make panel edit mode tooltip not unexpectedly disappear under certain circumstances

Summary:
The panel edit mode tooltip can currently disappear in an irritating manner under two circumstances:
- You need to mouse the mouse diagonally out of the configuration areat to reach the tooltop, because the timer's duration is very short
- You move the mouse between the tooltip and the configuration area in preparation for moving it to another applet, because the timer did not stop when moving from the tooltip to the configuration area

This patch fixes both issues by increasing the timer duration and stopping the timer when entering the configuration area

BUG: 413736
FIXED-IN: 5.18.4

Test Plan:
Edit the panel
Hover over an applet and move the mouse diagonally to its tooltip, crossing empty space
Hover over an applet and move the mouse back to the configuration area, then back to the applet, and back to the configuration area, then to another applet, then to that applet's tooltip

In both cases, the tooltip remains visible, as expected.

Reviewers: #plasma, broulik

Reviewed By: #plasma, broulik

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D27877