gopacket: SCTP chunk sub-decoder out-of-bounds panics on crafted segments

gopacket provides packet processing capabilities for Go. Prior to 1.7.2, the SCTP chunk chain in layers/sctp.go passes attacker-controlled declared lengths and counts to decodeSCTPInit, decodeSCTPShutdown, decodeSCTPError, decodeSCTPSack, and decodeSCTPParameter without checking that each chunk contains the fixed fields, parameter TLVs, gap acknowledgements, or duplicate TSNs those sub-decoders read. A crafted SCTP segment can therefore cause out-of-bounds or inverted slice panics; the panic can terminate applications that use gopacket.DecodeOptions.SkipDecodeRecovery, direct registered decoders, or DecodingLayerParser with IgnorePanic enabled, while the default recovery-enabled APIs convert it to a per-packet decode error. This is the SCTP sub-decoder residual named but not remediated by CVE-2026-65819, whose version 1.7.1 changes bounded the generic dispatcher but left these per-type reads and loops unchecked. The impact is availability only, with no data disclosure, modification, or allocation amplification. This issue is fixed in version 1.7.2.