[dartfuzz] Add support for simple recursion

Change-Id: I306d787dbcb154a3c51f13c9e01006d871a2213d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/126611
Commit-Queue: Fizaa Luthra <fizaaluthra@google.com>
Reviewed-by: Aart Bik <ajcbik@google.com>
Reviewed-by: Ben Konyi <bkonyi@google.com>

Author: Fizaa Luthra