Add refactored multiclient tests

[padelsbach]

This change is nearly entirely copied from the legacy tests. The rest is plumbing.

➜ diff ./test/wh_test_multiclient.c ./test-refactor/misc/wh_test_multiclient.c
21c21
<  * test/wh_test_multiclient.c
---
>  * test-refactor/misc/wh_test_multiclient.c
33c33,38
< #if defined(WOLFHSM_CFG_ENABLE_CLIENT) && defined(WOLFHSM_CFG_ENABLE_SERVER)
---
> /* Legacy test/wh_test.c gates the whTest_MultiClient() call site on
>  * !WOLFHSM_CFG_NO_CRYPTO. In test-refactor that gate has to live at the
>  * file level so the test reports SKIPPED rather than running an empty
>  * fixture under NOCRYPTO. */
> #if defined(WOLFHSM_CFG_ENABLE_CLIENT) && defined(WOLFHSM_CFG_ENABLE_SERVER) \
>     && !defined(WOLFHSM_CFG_NO_CRYPTO)
50a56
> #include "wh_test_list.h"
1423c1429
< static int whTest_MultiClientSequential(void)
---
> static int _whTest_MultiClient(void)
1646c1652
< int whTest_MultiClient(void)
---
> int whTest_MultiClient(void* ctx)
1648c1654,1655
<     return whTest_MultiClientSequential();
---
>     (void)ctx;
>     return _whTest_MultiClient();