Use PublicApiAnalyzers? #7421

Context: https://www.nuget.org/packages/Microsoft.CodeAnalysis.PublicApiAnalyzers/3.3.4-beta1.22403.2
Context: https://github.com/dotnet/roslyn-analyzers/tree/main/src/PublicApiAnalyzers

When we build src/Mono.Android, we use the microsoft.dotnet.apicompat tooling in order to compare the just-built Mono.Android.dll against a "reference" Mono.Android.dll; see e.g. 7840225.

This prevents us from breaking API by accident, but it doesn't prevent us from adding API by accident. (Though perhaps microsoft.dotnet.apicompat can do that too?)

There is a new Microsoft.CodeAnalysis.PublicApiAnalyzers NuGet package which can also be used for API compatibility purposes, and it can also check and error against API additions. This may be useful in ensuring that we only add API when we can safely do so (new API levels).