Check intraprocess_comm state

[CursedRock17]

This is a pull request targeting issue #689 (* Warning this is an older issue and the codebase has changed since then *). The point of that issue was just to expose the boolean for the intraprocess_comm subscription state, which looks like this:

enum class IntraProcessSetting
{
  /// Explicitly enable intraprocess comm at publisher/subscription level.
  Enable,
  /// Explicitly disable intraprocess comm at publisher/subscription level.
  Disable,
  /// Take intraprocess configuration from the node.
  NodeDefault
};

but both the Publisher and Subscription have protected bools: intra_process_is_enabled_ and use_intra_process_ respectively, which showcase if state can be used for intraprocess communication.

While this code was just meant to address the problem in the issue, the create_publisher and create_subscription functions have changed in the 4 years it's been since the original issue that the issue this PR addresses, was meant to fix. They no longer have IntraProcessSetting use_intra_process_comm = IntraProcessSetting::NodeDefault); in their function defintions, which makes adding the tests a bit more difficult for the context of the problem since it's not the same. I think the functions are still perfectly useful in the base classes and for querying, just don't know how to go about testing now, since they aren't complex functions.

[CursedRock17]

Friendly Ping, was that NodeDefault Test enough, or should I extend it further?