Update S3962: Ignore public static readonly fields

[sl-williamdiesny]

Description

The solution proposed by the rules S3962 and S2339 are not compatible.

Rule S3962 : Change static readonly into const,
Rule S2339 : Change public constant into static readonly.

I think the rule S3962 should be applied only on non public constant.

[michalb-sonar]

Thanks for reporting @williamdiesny. That's a good suggestion.

[sl-williamdiesny]

I made a pull-request, hope this help...

#609

[MaxTranced]

IMHO S3962 should also ignore internal visibility fields if the containing assembly is using
[assembly: InternalsVisibleTo("AnotherAssembly")]
This is probably an infrequent case, just thought I'd mention it here to get thoughts.

[valhristov]

@MaxTranced we thought about that when we developed the fix, but it is rather difficult to check for assembly attributes from an analyzer that works on class level. It could be done, but in exchange for significant complexity increase...

[MaxTranced]

@valhristov that makes sense. Thank you!