Add a new RSxxxx diagnostic to our MS.CA.Analyzers package to flag descriptors being used to report a diagnostic that do not have the CompilationEnd custom tag: https://github.com/dotnet/roslyn/blob/440b6fc370f0ddcea68b445e183f1383c0d1bc6e/src/Compilers/Core/Portable/Diagnostic/WellKnownDiagnosticTags.cs#L56 custom tag

See dotnet/roslyn#65304 (comment) for details