If a reference exists that has a virtual method with a ref-readonly parameter and [IsReadOnly] attribute, but no [IsConst] required modifier: Per feature design this is not possible, but it can be created by external tools/compilers. Should it be imported and used in the compilation? or should we mark it as a bad symbol and generate a use site error for it?

This issue should track design decisions taken around this issue, and how to fix it.
Issue was raised in #19658, where the PR for now allows it and added tests to verify the behavior.

cc @AlekseyTs @VSadov