Analyzer to flag invocations of [Pure] methods as an ExpressionStatementSyntax

[AArnott]

Define (or find and depend on) an analyzer to call out when [Pure] methods are called without doing anything with their result.

[AArnott]

It looks like dotnet/roslyn-analyzers#747 already defines CA1806 in the Microsoft.Maintainability.Analyzers package.

[AArnott]

But sadly, that analyzer doesn't work: dotnet/roslyn-analyzers#1845