DDC's codegen test copies those files to a local "gen" directory so
that it can do stuff like splitting out the multitests before it
compiles them to JS.
I left all of that alone, so the rest of DDC's test infrastructure is
unchanged. The very first step that builds the "gen" directory just
copies from sdk/tests/..._strong/... instead and the rest is good to go.
I did not move not_yet_strong_tests.dart somewhere more accessible yet
because I'm not sure if kernel needs it or where it should go.
I did not create any status files because DDC doesn't need them and
there are no test suites for the new directories for the other
platforms.
Bob Nystrom
6c757957db