Added noise blur effect

Summary:
Added the option to turn on noise behind the blurred area.
The lowest strength value disables it completely, so it is optional and is disabled by default.

Test Plan:
Edit: this new screenshot shows the updated noise generation.
Edit2: separated the screenshots so you can flick through them to clearly see the differences

Reviewers: KWin, VDG, fredrik

Reviewed By: VDG, fredrik

Subscribers: davidedmundson, matheusm, romangg, ivan, zzag, ngraham, kwin, KWin

Tags: KWin

Differential Revision: https://phabricator.kde.org/D10281