Replace JGSS implementation to use native GSS-API where available

Since JDK 12 (and backported to 8u371+ = April 2023), the JDK ships its own native GSS-API bridge for Windows (SSPI-backed), giving Kerberos/SPNEGO single sign-on without a third-party library.

The connector currently only supports this via waffle-jna (JAAS/Krb5LoginModule-based) or falls back to a pure-Java ticket-cache implementation that can't do true Windows SSO.
This targets 3.6 to re-evaluate the GSSAPI authentication path, favoring the JDK's built-in native bridge where the runtime supports it, reducing reliance on the third-party dependency.