Summary:
There are several reasons why I "re-wrote" the Glide effect:
* it doesn't work correctly because it suffers from undesired perspective distortions: {F5914378}
   The worst part is that windows are distorted so much on multiple monitor setups that it's hard to say whether that's glide animation.
* window close animation is not quite intuitive: if the close button is
  located at the top and I click it, I would expect that window is
  rotated around the bottom edge, not the top; (IMHO)
* it's too much distracting when working on something for quite good
  amount of time: e.g. when editing photos, which involves a big number
  of different dialogs;
* there are issues with deletion of QTimeLine;
* windows are not gracefully released if some other effect grabs them;
* its code doesn't follow common coding style in KWin.

So, the "new" Glide effect is more subtle, it's possible to have
different rotation edges for window open/close animations, it doesn't
animate special windows(like audio volume feedback), the code is simpler
and readable. Yet, there are some issues with QTimeLine, which are
common to all effects in KWin anyway.

### Demos

{F5889803}
//Window Open Animation//

{F5889804}
//Window Close Animation//

{F5889805, layout=center, size=full}
//KCM//

CCBUG: 394245

Test Plan:
* Enabled the Glide effect
* Closed System Settings
* Opened it again

Reviewers: #kwin, #plasma, #vdg, davidedmundson

Reviewed By: #kwin, #plasma, #vdg, davidedmundson

Subscribers: ngraham, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D13338