Diagnostic for use of plain protocol name in type position should suggest `some` or `any`

The following code is invalid:

protocol P {
  associatedtype A
}

func generic(value: P) {}

The compiler currently produces the error message Use of protocol 'P' as a type must be written 'any P' with a fix-it to insert the any keyword.

However, a different (and often better!) fix here is to use the some keyword. The error message should be re-worded to prompt the programmer to consider any or some, and there should be two notes, each with a fix-it to insert any or some, respectively.