v9: make -e and -c use function impl for processing (a la -E/-C)

I.e. vm.runInNewContext is deprecated (supported with JSON_EXEC=vm
envvar), -E/-C are deprecated (just go back to using -e/-c). Backward
incompat because of the semantic changes on `CODE` arg. The main
semantic change is the need to use `this.` for accessing the
object being processed.