In addition to oss-fuzz's CIFuzz (see #7052), this commit adds a small
shell script that run all fuzzing tests with go test -fuzz.
While running for 30 seconds would be too short to acutally find issues,
we want to make sure that these fuzzing tests are not fundamentally
broken.
Signed-off-by: Kazuyoshi Kato <katokazu@amazon.com>
