Figure out if
* we're missing enum values (easy to workaround, but annoying for developers)
* we expose enum values that are not defined natively (potential bugs)
reference: https://github.com/xamarin/xamarin-macios/issues/7527
backport of #9691 with additional macOS and xcode12.2 fixes
* [fileprovider] Update for Xcode 12 beta 6
This was quite noisy. Apple removed all API marked as
`FILEPROVIDER_API_AVAILABILITY_V3`.
```
```
Most were bound but they were (majority) decorated with `[NoiOS]` and
`[NoMac]` so they did not generated any bindings.
A few of them were modified or just became macOS-only.
Deprecation warnings also needed to be updated.