1) Don't reset LUT docker when moving the window over screens. We should
   actually check if the combo boxes contents is going to change or not in
   resetOcioConfiguration() and keep them intact if possible for not
   resetting the user's settings.

BUG:373481

2) The display shader should be recompiled not when setDisplayFilter() is
   called, but when filter->updateShader() is called. The point is that
   quite a lot of filter updates happen without(!) recompiling the shader.
   And, obviously, the order of calls to updateShader() and
   setDisplayFilter() is generally undefined, so if we try to recompile it
   in setDisplayFilter() there might be still outdated version of it.

3) Removed explicit initialization of the display filter in
   LutDockerDock::setCanvas(). The point is that the correct filter will
   be correctly initialized later in updateDisplaySettings(). And this
   extra call made Krita recompute the image 6(!) times when loading any
   image. That can take ages on complex images like miloor_turntable_002.kra