Enabling this will ensure that future bindings (and Xcode updates that
change nullability information) are spotted right away.
The binding fixes are **not** complete, i.e. what was done was mostly
to debug the xtro rule and find corner cases. The backlog will be
_ignored_ so the builds won't fail.
This should let us provide a nicer API for the GM change about
`CBManager authorization` moving from an instance to a static
property (in all but iOS 13.0 / watchOS 6.0)
* 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.