Make the fuzzer use FuzzedDataProvider.

Change-Id: I1af4f8d9b5b24b46d7bf74339b1fb667bcbe235f
Reviewed-on: https://code-review.googlesource.com/c/re2/+/51051
Reviewed-by: Paul Wankadia <junyer@google.com>
(cherry picked from commit 6c109e908aa4006c0cd147d2397023b7b8f2705d)
Reviewed-on: https://code-review.googlesource.com/c/re2/+/51230