Fix tooltip woes

Summary:
Users have reported a number of bugs against TM tooltips, e.g. initially
coming up with crazy sizes, or showing window duplicates. This all comes
down to a race conditions causing stale data and ugly code that's using
visible props to swap between two alternate UI implementations instead
of doing clean conditional loading.

With this cleanup patch the problems should be gone, as well as various
ReferenceErrors spewed onto the tty.

BUG:382571
BUG:385947
BUG:389469
BUG:388749

Reviewers: broulik, davidedmundson, romangg

Reviewed By: davidedmundson

Subscribers: rikmills, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D13602