Allow messages published on $JS.EVENT.ADVISORY.API to be exported via a service

[piotrpio]

Use case:

I want to aggregate JetStream advisory events from multiple accounts on one aggregate account. This would allow nats-surveyor to maintain a single connection with the server to gather JetStream advisory metrics from multiple accounts.

I have the following config:

jetstream: {max_mem_store: 64GB, max_file_store: 10TB}
accounts {
	A {
		jetstream: enabled
		users: [ {user: pp, password: foo} ]
		imports [
			{ service: { account: AGG, subject: '$JS.EVENT.ADVISORY.ACC.A.>' }, to: '$JS.EVENT.ADVISORY.>' }
		]
	}
	AGG {
		users: [ {user: agg, password: foo} ]
		exports: [
			{ service: '$JS.EVENT.ADVISORY.ACC.*.>', response: Singleton, account_token_position: 5 }
		]
	}
}

Intended behavior

1. On JetStream events, server publishes messages on $JS.EVENT.ADVISORY.> in account A.
2. Account AGG exports a service with account_token_position on which the advisory events should be forwarded
3. All advosory messages from account A should be available on $JS.EVENT.ADVISORY.ACC.A.>

Actual behavior
Advisory events published on subjects other than $JS.EVENT.ADVISORY.API (e.g. $JS.EVENT.ADVISORY.STREAM.CREATED.ORDERS) are mapped correctly and available on account AGG. Messages published on $JS.EVENT.ADVISORY.API (the audit messages) are not available on AGG.

Additional information

• Behavior is the same whether or not mapping is used, e.g. exporting $JS.EVENT.> -> $JS.EVENT.> does not fix the issue
• Intended behavior can be achieved using stream export from account A to account AGG and in that case it works fine (I can subscribe on $JS.EVENT.ADVOSORY.ACC.A.> and all events are available. However, using service exports would be a desirable solution since with services I can utilize account_token_position and have a single export on account AGG instead of an import per account.
• This seems to be caused by some advisory events being published using Server.sendInternalAccountMsg() (those are not forwarded) - https://github.com/nats-io/nats-server/blob/main/server/jetstream_api.go#L4332C29-L4332C29
• The same behavior is present when attempting to export service latency subjects (which also uses sendInternalAccountMsg())
• I am not sure whether this behavior is intentional or not, but seems to be inconsistent given it differs depending on whether stream export or service export is used.

I added a test to show the issue: 3b19e16
The first test (TestJetStreamAccountImportJSAdvisoriesAsService) uses service exports (and fails) and the second uses stream exports (which succeeds). Both tests have the same scenario:

1. On account JS, subscribe to $JS.EVENT.ADVISORY.>
2. On account AGG, subscribe to $JS.EVENT.ADVISORY.ACC.JS.>
3. Create a stream on account JS
4. Expect two messages on both subscriptions:

• an action event on $JS.EVENT.ADVISORY.STREAM.CREATED.ORDERS
• an api audit event on $JS.EVENT.ADVISORY.API