AST: Implement TypeBase::getContextSubstitutions() for tuple types
AST: Implement TypeBase::getContextSubstitutions() for tuple types

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