make the existing general import predicates value specific and introduce type specific equivalents

[felixarntz]

Pull Request Description

• The recently added importFromParents, importFromCurrentDir, and importFromExternals predicates so far handled both value imports and type imports.
• This is not ideal because type imports may have different implications than value imports.
• It's also inconsistent with how we already had import and importTypes predicates, with the former only covering value imports.
• This PR modifies those 3 new predicates to only handle value imports, and introduces equivalent importTypesFromParents, importTypesFromCurrentDir, and importTypesFromExternals predicates.