Move the warnings/error settings up to the project level
Move the warnings/error settings up to the project level

The settings were only on some of the iOS targets, move them all up to the
project level so they are consistent between the iOS and macOS targets.

Some of the testings might not apply (ObjC, etc.), but go ahead and leave them
raised just incase someone goes scanning.

apple/swift-protobuf,tbkka/swift-protobuf,thomasvl/swift-protobuf,cburrows/swift-protobuf,tbkka/swift-protobuf,cburrows/swift-protobuf,thomasvl/swift-protobuf,thomasvl/swift-protobuf,apple/swift-protobuf,allevato/swift-protobuf,allevato/swift-protobuf,apple/swift-protobuf,apple/swift-protobuf,apple/swift-protobuf,tbkka/swift-protobuf,tbkka/swift-protobuf,allevato/swift-protobuf,tbkka/swift-protobuf,allevato/swift-protobuf,allevato/swift-protobuf,allevato/swift-protobuf,cburrows/swift-protobuf,allevato/swift-protobuf,cburrows/swift-protobuf,apple/swift-protobuf,thomasvl/swift-protobuf,cburrows/swift-protobuf,cburrows/swift-protobuf,tbkka/swift-protobuf,cburrows/swift-protobuf,tbkka/swift-protobuf,thomasvl/swift-protobuf,thomasvl/swift-protobuf,thomasvl/swift-protobuf,apple/swift-protobuf