Expose ActivateSession service result on UaSession

[kevinherron]

Summary

Expose the most recent successful ActivateSession service result through UaSession so client code can observe advisory Good_* outcomes such as Good_PasswordChangeRequired after a session is established or reactivated.

• Add UaSession.getLastActivateSessionServiceResult() and back it with OpcUaSession so callers can inspect the latest successful ActivateSession status without reaching into lower-level protocol objects.
• Update the session FSM to record the ActivateSessionResponse service result on both initial activation and reactivation so the session reflects the server's latest accepted response.
• Add integration coverage for the default success case and for advisory-good responses such as Good_PasswordChangeRequired, using a delegating test service set to customize ActivateSession responses.

Key Changes

• Session API surface: UaSession now exposes an optional last ActivateSession service result, which keeps the API backward compatible for session implementations that do not populate it.
• Session lifecycle tracking: SessionFsmFactory stores the service result after both initial activation and reactivation so the session reflects the latest successful server response.
• Integration test harness: Add a delegating session service set for tests so ActivateSession responses can be overridden without replacing the default session service implementation.

Testing

• ActivateSessionServiceResultTest verifies that a connected client session exposes a present, good ActivateSession service result after connect.
• ActivateSessionServiceResultOverrideTest verifies that advisory good codes returned by ActivateSession, including Good_PasswordChangeRequired, are preserved on the client session.
• Verification command: mvn -q clean verify

References

• Discussion #1729: Expose ActivateSession service result (Good_PasswordChangeRequired) to client code