Improve Subscription features and fix IntraTransport discovery

[johnwason]

This PR does the following:

• Add the UpdateServiceByType() to ServiceSubscription to allow for the desired search types and the filter to be updated without creating a new subscription.
• Add Attributes filter to the ServiceSubscriptionFilter. This will allow for more flexibility in designing node filters without requiring a custom callback function.
• Fix the node discovery in IntraTransport that was not working properly. Add the StartClient() function to enable discovery correctly.
• Fix bug with ServiceSubscriptionClientID taking a reference to NodeID instead of copying in wrappers, leading to a segfault.
• Add subscription tests using IntraTransport