GHSA-cf4g-fcf8-3cr9: `pnet_packet` buffer overrun in `set_payload` setters

The vulnerability explicitly affects set_payload setters generated by the packet macro in pre-0.27.2 versions. While specific struct names aren't provided in the advisory, the core issue lies in the macro's code generation for mutable packet implementations. The PR #455 fix in the macro confirms that all set_payload methods generated by this macro were vulnerable to buffer overruns due to improper payload length handling. The high confidence comes from the direct correlation between the vulnerability description, the fix location, and the nature of macro-generated setters affecting multiple packet types uniformly.