[Sema|NFC] Refactor findInconsistentImports
[Sema|NFC] Refactor findInconsistentImports

Break findInconsistentImportsAcrossFile into two services, one finding
inconsistencies across a whole module and a new one finding them across
a single file.

roambotics/swift,glessard/swift,apple/swift,roambotics/swift,glessard/swift,apple/swift,apple/swift,roambotics/swift,glessard/swift,glessard/swift,glessard/swift,apple/swift,roambotics/swift,apple/swift,apple/swift,roambotics/swift,roambotics/swift,glessard/swift