coap_openhitls.c: prefer SAN before CN for certificate names

[tlhc]

Add prefer SAN before CN for certificate names

[Copilot]

Pull request overview

Updates the openHiTLS TLS backend to prefer certificate Subject Alternative Name (SAN) DNS entries over the Subject Common Name (CN) when deriving the peer “name” used for callback validation and SNI mismatch checks, aligning behavior with modern certificate validation expectations.

Changes:

• Add openHiTLS helper logic to extract DNS SAN first and fall back to CN when SAN is unavailable.
• Extend TLS backend test script with SAN-preferred and CN-fallback PKI test cases and certificate generation.
• Update the pinned openHiTLS commit reference used by CI.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/coap_openhitls.c	Implements SAN-first name extraction (with CN fallback) for openHiTLS certificate name handling.
examples/tls_backend_testcases.sh	Adds PKI cert generation and test cases covering SAN preference and CN fallback.
.github/workflows/main.yml	Updates the pinned openHiTLS commit used during CI builds.

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[mrdeep1]

LGTM