dcsctp: Add SCTP packet corpus

Each file is a SCTP packet (without any additional headers), all
extracted from a few Wireshark dumps that have been manually recorded.

Bug: webrtc:12614
Change-Id: I64bef0c563f1d83ae22735d702c8abafec6429b9
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/214701
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33675}

test/fuzzers/BUILD.gn

@@ -620,6 +620,7 @@ webrtc_fuzzer_test("dcsctp_packet_fuzzer") {
     "../../net/dcsctp/packet:sctp_packet",
     "../../rtc_base:rtc_base_approved",
   ]
+  seed_corpus = "corpora/sctp-packet-corpus"
 }
 
 webrtc_fuzzer_test("rtp_header_parser_fuzzer") {

test/fuzzers/corpora/README

@@ -32,3 +32,6 @@ is used for this.
 
 ### PseudoTCP ###
 Very small corpus minimised from the unit tests.
+
+### SCTP ###
+This corpus was extracted from a few manually recorder wireshark dumps.