Add VM transport broker restart test

[pradeep85841]

This PR adds a unit test to validate VM transport behaviour when the broker
is stopped and restarted.

The test ensures:

• Messages can be sent and received before broker shutdown
• A restarted broker correctly accepts new VM transport connections
• No stale broker registry state affects message delivery

Test passes when run in IDE and follows existing ActiveMQ unit test patterns.

[jeanouii]

Out of curiosity, is this test because you have seen some weird behavior or because you faced issues with the VM transport?

Nothing critical, but FYI there are discussions to get rid of Spring, so it'd be nice to use Plain JMS APIs instead of JmsTemplate to ease future work to remove Spring. It's probably not of a big value here, so maybe something you can do. Again, not critical.

[jeanouii]

Thank you for addressing the small feedback.

[jbonofre]

Thanks for the test.

nit: as this test is "squared" on vm, it would have make sense to add the test in the activemq-broker module (instead of activemq-unit-tests).
But that's a detail, and we can move it later.

[jbonofre]

I just ran the CI. I will merge as soon as green.