shell: add org.gnome.Shell.Introspect interface

GNOME Settings Daemon now uses org.gnome.Shell.Introspect D-Bus
interface to enable/disable animations.

gnome-settings-daemon!135
3 jobs for master in 15 minutes and 6 seconds
Status Job ID Name Coverage
  Validate
passed menu #693190

00:01:01

 
  Build
passed ubuntu #693191

00:14:05

 
  Analysis
manual coverity #693192
allowed to fail manual