Fix DoRequestSuccess and DoRequestFailure, Add regress test

[yosuke-wolfssl]

RFC 4254 §4 defines SSH_MSG_REQUEST_SUCCESS as byte SSH_MSG_REQUEST_SUCCESS followed directly by response-specific data (with no length prefix).
This PR fixes DoRequestSuccess and DoRequestFailure so that these don't consume the data with length prefix.
Also, this adds the regress test.

[Copilot]

Pull request overview

Fixes parsing of SSH_MSG_REQUEST_SUCCESS / SSH_MSG_REQUEST_FAILURE payloads to match RFC 4254 §4 (payload is message-specific data with no length prefix), preventing buffer overruns during packet consumption, and adds a regression test to cover the scenario where the success payload is a raw uint32 port.

Changes:

• Update DoRequestSuccess() / DoRequestFailure() to advance the payload index by len (payload size) rather than parsing a length-prefixed field.
• Add a regression test that feeds a SSH_MSG_REQUEST_SUCCESS packet with a uint32 port payload and asserts DoReceive() succeeds.
• Wire the new regression test into the regress test runner.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/internal.c	Corrects request success/failure payload consumption logic to avoid interpreting payload data as a length prefix.
tests/regress.c	Adds and executes a regression test ensuring SSH_MSG_REQUEST_SUCCESS with a uint32 payload parses successfully.

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