macosx: Move library subview setup code out of VLCLibraryWindow and into relevant view controller classes
We do a lot of things in VLCLibraryWindow relating to setting up subview insets and spacings, originally to ensure that measurements were consistent. Thanks to VLCLibraryUIUnits we no longer need to do this and can move this code into the view controller classes where it belongs, decluttering VLCLibraryWindow and refocusing its scope onto setting up VLCLibraryWindow and its direct subviews
Signed-off-by: Claudio Cambra developer@claudiocambra.com