Add tests for DoUserAuthRequestRsa and DoUserAuthRequestRsaCert

[yosuke-wolfssl]

This PR adds the tests for DoUserAuthRequestRsa and DoUserAuthRequestRsaCert to exercise RSA signature verification path and certificate verification accordingly.
Addressed by f_4584

[Copilot]

Pull request overview

This PR extends the tests/auth.c authentication test harness to add new negative/positive test coverage for RSA public-key authentication and RSA X.509 certificate-based public-key authentication, specifically exercising the RSA signature verification paths (DoUserAuthRequestRsa / DoUserAuthRequestRsaCert) and certificate chain verification.

Changes:

• Extend the auth test server thread arguments and pubkey server context to optionally carry a CA certificate and a configurable userAuth callback.
• Add an RSA “bad signature” test that signs with a different private key while presenting the authorized public key (ensuring signature verification fails past the authorized-key hash check).
• Add RSA X.509 cert auth tests (success + bad signature) gated behind the relevant certificate/RSA/SHA1-related compile-time macros.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
tests/auth.h	Extends thread_args to include an optional server userAuth callback and optional CA cert buffer info for cert-based auth tests.
tests/auth.c	Adds RSA bad-signature and RSA cert auth tests; updates pubkey server thread to optionally register a CA cert and to take the userAuth callback from thread_args.

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[wolfSSL-Fenrir-bot]

Fenrir Automated Review — PR #992

No scan targets match the changed files in this PR. Review skipped.