BannedApiAnalyzers: Support banning base types

[aelij]

Fixes #6841

Note I've had to change XUnitVerifier to DefaultVerifier due to the following exception:

  Error Message:
   System.MissingMethodException : Method not found: 'Void Xunit.Sdk.EqualException..ctor(System.Object, System.Object)'.
  Stack Trace:
     at Microsoft.CodeAnalysis.Testing.Verifiers.EqualWithMessageException..ctor(Object expected, Object actual, String userMessage)
   at Microsoft.CodeAnalysis.Testing.Verifiers.XUnitVerifier.Equal[T](T expected, T actual, String message) in /_/src/Microsoft.CodeAnalysis.Testing/Microsoft.CodeAnalysis.Testing.Verifiers.XUnit/XUnitVerifier.cs:line 49

See dotnet/roslyn-sdk#1099 (comment)

[codecov]

Codecov Report

Merging #7052 (5997981) into main (cc67474) will decrease coverage by 0.01%.
The diff coverage is 84.05%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7052      +/-   ##
==========================================
- Coverage   96.43%   96.43%   -0.01%     
==========================================
  Files        1412     1412              
  Lines      336560   336629      +69     
  Branches    11119    11123       +4     
==========================================
+ Hits       324558   324613      +55     
- Misses       9201     9213      +12     
- Partials     2801     2803       +2     

[drewnoakes]

Nice!