This should take care of all the remaining CA1416 errors.

Here's what I found about the analyzer for this -
* It understands when code from Xamarin/macios is reachable from maui
code and will flag an error
* It never understands the pattern `if
(!OperatingSystem.IsZZZZZZVersionAtLeast(major, minor)) return;` that
implies that the rest of the code in the method is safe, flagging a
false failure
* Compound OS tests or complex code inside the test will flag a false
failure
* In the case of [this
code](https://gist.github.com/stephen-hawley/716761d318fbcddd7795ed53d331cdc8),
the analyzer appears to hang, although to be clear, I don't have
evidence that it is the analyzer doing this

In order to work around this, the simplest way is to refactor all the OS
version specific code into its own method and flag it with
`[SupportedOSPlatform("xxxyy.zz")]`. In this case, the above false
failures go away.

In rare cases, I was unable to do this and instead used a `#pragma` to
suppress the warning around the code that triggered the false failure. I
tried to avoid this at all costs since this is source of bugs waiting to
happen.