Apple Cert Fix: Prevent verify callback from blocking ANCV invocation

[bigbrett]

Fixes issue reported in 9604

Description

When system certificate store support is enabled on Apple platforms, wolfSSL is intended to fall back to Apple’s native trust APIs if verification against the wolfSSL CA bundle fails. However 9144 introduced a regression such that the Apple native validation routine never gets invoked if a user-provided verification callback is set and returns success. The verification result was overwritten before the Apple native validation check, preventing the fallback.

This PR fixes the regression in behavior and further improves the apple cert check integration

ProcessPeerCerts()
        |
        v
[TLS_ASYNC_BEGIN] - Parse cert chain into buffers
        |
        v
[TLS_ASYNC_BUILD] - Process intermediate certs (count-1 to 1)
        |
        |   For each intermediate cert:
        |     1. ProcessPeerCertParse() - validate cert
        |     2. ANCV bypass for ASN_NO_SIGNER_E (clears error)
        |     3. DoVerifyCallback() - callback can override/reject
        |     4. On fatal error: break loop, send fatal alert
        |
        v
[TLS_ASYNC_DO] - Process leaf cert (certIdx = 0)
        |
        |   1. ProcessPeerCertParse() - validate leaf
        |   2. If ASN_NO_SIGNER_E && ANCV enabled:
        |      - DoAppleNativeCertValidation() <--- Attempt to verify chain using Apple SDK
        |      - If success: ret = 0
        |   3. If ret != 0:
        |      - DoVerifyCallback() (sets leafVerifyErr)
        |   4. If ret != 0, send fatal alert and exit
        |
        v
[TLS_ASYNC_VERIFY] - OCSP/CRL, key usage, domain checks (internal to wolfSSL, only run on successful trust eval)
        |
        v
[TLS_ASYNC_FINALIZE]
        |
        |   1. Load lastErr if ret == 0
        |   2. DoVerifyCallback() if not already called for leaf
        |   3. Handle verifyNone for CRL errors
        |   4. Send alert if ret != 0 && !verifyNone
        |
        v
[TLS_ASYNC_END] 

# Checklist

 - [ ] added tests
 - [ ] updated/added doxygen
 - [ ] updated appropriate READMEs
 - [ ] Updated manual and documentation

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