Fix Platform Compatibility Code Analysis Violations

[pjcollins]

Context: #796

Remove the dotnet_diagnostic.CA1416.severity = none rule from .editorconfig and build locally to see a list of platform compatibility code analysis violations.

Binlogs for warnings treated as errors from initial .NET 6 preview 4 bump
binlogs.zip

Additionally, the BI1234 warnings in Essentials-net6 should be fixed.

[mattleibow]

Just did another run and this is still got stacks of warnings.

But, things are a bit weird for iOS. Since Apple marks things as deprecated, we get warning s saying that a method is unsupported on say iOS 14, so I am not sure how we are to express this in code.

void DoThing()
{
    if (on14AndLater)
        DoNewThing();  // warning: this is only available on 14+
    else
        DoOldThing();   // warning: this is not available on pre-14
}

[mattleibow]

Hah! I see the new OperatingSystem.IsIOSVersionAtLeast or OperatingSystem.IsOSPlatformVersionAtLeast("ios", 14, 0) is incredibly smart!

Amazing! We should do this!

[hartez]

Hah! I see the new OperatingSystem.IsIOSVersionAtLeast or OperatingSystem.IsOSPlatformVersionAtLeast("ios", 14, 0) is incredibly smart!

Amazing! We should do this!

So this, then? #461