This now formal `CAAnimationDelegate` protocol had to be reverted [1]
because we did not support `FormalSince` at the time - and this broke the
static registrar when used with older SDK. Support was added in [2] but
did not include `CAAnimationDelegate` (but `CALayerDelegate` was fixed).
Because this was not a protocol the `Delegate` property expose it as a
`CAAnimationDelegate`, the concrete/model type, and not an interface.
The workaround so `ICAAnimationDelegate` can be used, thru the
`WeakDelegate`, requires to manually re-bind some API because the
generator won't allow this anymore (it's bad to expose a [Model]
when a [Protocol] exists).
xtro data updated
[1] https://github.com/xamarin/xamarin-macios/pull/698
[2] https://github.com/xamarin/xamarin-macios/pull/2130
* Not every old annotations have been migrated (work in progress, to be completed in another PR);
* Sanitation of the data files (e.g. removal of dupes and fixed, by Apple, entries) is done, but not automated (also a work in progress)
Even then this is immediately useful, i.e. better merged before 15.6 gets branched.