SA1000 doesn't handle checked operator definitions

[tannergooding]

C# 11 is introducing user-defined checked operators (public static T operator checked +(T value);) and currently triggers SA1000 saying no space is expected after checked.

The analyzer should be updated to allow a space when checked is used in this context, seeing as it differs from the normal checked(expr) syntax.

[tannergooding]

This is triggering various warnings for dotnet/runtime when trying to implement the generic math feature and so I've worked around it by switching the analyzer to suggestion.

[bjornhellander]

@tannergooding, is this available in a preview yet? I can't get an example class to compile using the new syntax.

[tannergooding]

I believe it went out in .NET 7 Preview 3, but it might need a nightly or to wait until .NET 7 Preview 4 if I've got my dates mixed up.

[bjornhellander]

This looks simple to fix, but I did not manage to get a unit test to compile my test code using Microsoft.CodeAnalysis.CSharp.Workspaces 4.2.0-4.final. Waiting until the next release of that package.