feat: warn when SwiftSyntaxMacrosTestSupport is used with Swift Testing (#3190)#3217

DPrakashhh wants to merge 1 commit intoswiftlang:mainswiftlang/swift-syntax:mainfrom

DPrakashhh:task/3190-swift-testing-warningDPrakashhh/swift-syntax:task/3190-swift-testing-warningCopy head branch name to clipboard