[dart/fuzzer] Fuzz support for spread and control flow collections
[dart/fuzzer] Fuzz support for spread and control flow collections

Rationale:
Follows the documented grammar to allow for arbitary nested
spead/if/for inside collections (list, set, maps).

https://github.com/dart-lang/sdk/issues/36218
https://github.com/dart-lang/sdk/issues/36214

Change-Id: Ie5b5828a323401c4db14045e6edd0587677f2c19
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/98261
Reviewed-by: Aart Bik <293afa0533434225484ba3f9bf2859340baba6ea@google.com>
Reviewed-by: Vyacheslav Egorov <72c81f38df725d8f1832acb9b5bb99563fc2f1b9@google.com>
Reviewed-by: Siva Annamalai <2e618a8cbd7bb6b3d4409061ae407d692a098546@google.com>
Commit-Queue: Aart Bik <293afa0533434225484ba3f9bf2859340baba6ea@google.com>

dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk