Add async support for RSA

[bigbrett]

no description needed

[Copilot]

Pull request overview

This PR adds an asynchronous (request/response) API surface for RSA operations in the wolfHSM client, and refactors existing blocking RSA wrappers to build on those async halves. It also extends the crypto test suite to exercise the new async RSA APIs and keygen flows.

Changes:

• Introduces async request/response functions for RSA function, key-size query, and key generation (cache + export).
• Refactors the blocking RSA keygen/function/get-size wrappers to reuse the new async response handlers.
• Adds a dedicated RSA async API test that covers success paths and key argument validation/buffer-size behavior.

Reviewed changes

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

File	Description
wolfhsm/wh_client_crypto.h	Adds public async RSA API declarations and Doxygen documentation.
src/wh_client_crypto.c	Implements async RSA request/response halves and refactors blocking wrappers to reuse them.
test/wh_test_crypto.c	Adds an async RSA API test and hooks it into the client crypto test run.

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[wolfSSL-Fenrir-bot]

Fenrir Automated Review — PR #381

Scan targets checked: wolfhsm-core-bugs, wolfhsm-crypto-bugs, wolfhsm-src

No new issues found in the changed files. ✅

[Frauschi]

LGTM. Only nit I found: the async documentation is not updated, but that would only move the RSA methods from "Roadmap" to "Done". Handle this as you see fit.

[bigbrett]

@Frauschi stopped updating the draft doc because I have another PR that is completely rewriting ALL documentation :)