Defines the %target-playground-build-run-swift macro in the local lit config for PlaygroundTransform which contains all the boilerplate code used by most PlaygroundTransform tests:
* Build a PlaygroundSupport module
* Build the test source into an executable, linking PlaygroundSupport
* Codesign and run the executable
When ImplicitOpenExistentials was enabled (default in Swift language mode 6) the Instrumenter would crash the compiler when building logger calls. This was due to an incorrect assumption that the newly created apply expr wouldn't change type when type-checked. However, the type checker is free to change the kind of expression and did so in circumstances where the call expr was wrapped in an open existential expr.
