NSView.AddToolTip should offer an overload with an NSObject owner

[sandyarmstrong]

Previously, AddToolTip only allowed sending an NSObject as owner. Now, it only allows sending an INSToolTipOwner. Both should be allowed. According to the docs, the owner is

An object from which to obtain the tooltip string. The object should either implement view:stringForToolTip:point:userData:, or return a suitable string from its description method. (It can therefore simply be an NSString object.)

It feels like too much ceremony to have to implement INSToolTipOwner when before we could just pass NSString, which satisfies the second option according to Apple.