…xContext.

Move IMarshallingGeneratorFactory creation into LibraryImportGenerator.
Create InteropAttributeData base type for attribute info.
Better represent how to ensure incrementality with IMarshallingGeneratorFactory instances without making them IEquatable themselves.

…pper around DllImport.

Create extension methods to use in IIncrementalGenerator implementations

Use an extension method to report diagnostics easily.

…ators that have specific requirements require less copy-paste.

…incremental tests changed as the tree traversal that records all of the steps was recording the cases that reported diagnostics first.

Update the incremental tests to not report diagnostics to ensure that step order matches SyntaxTree order.

…l it into the context type we pass)