The STUN fuzzer is split into two parts: validation and parsing. The
latter should be able to handle invalid packets instead of assuming
the validation deals with them, since an adversary could set a valid
HMAC on an invalid packet.
NOTRY=true
Review-Url: https://codereview.webrtc.org/2044523002
Cr-Commit-Position: refs/heads/master@{#13050}