Related error spans for assignability checks #25030
Description
Now that we support multiple related spans for errors (#10489, #22789, #24548), we'd like to improve an existing error message.
Currently we have the following error for assignability checks:
Type '{0}' is not assignable to type '{1}'.
Type '{0}' is not assignable to type '{1}'. Two different types with this name exist, but they are unrelated.
@weswigham had some ideas to iterate on these error messages.