feat(tls): add SANs support for both DNS-names and URIs

[lucab]

This adds two new Lua functions (and the corresponding C logic) to configure custom SANs validation in nginx:

• resty.kong.tls.set_upstream_ssl_sans_dnsnames()
• resty.kong.tls.set_upstream_ssl_sans_uris()

Part of KAG-6247.

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Notes:

• This requires a corresponding nginx patch implementing the additional TLS-name validation logic.
• Testing for this change (and the above nginx patch) is done at the integration level in Kong, see linked PR.

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