Add support for setting service bus max message size

[MartinWa]

The changes in this PR are as follows:

• For a Service Bus Topic it adds the max_message_size property. This allows configuring the large messages feature in premium subscriptions.
• Updated Microsoft.Azure.Management.ServiceBus to version 5.0.0 to support this setting

I have read the contributing guidelines and have completed the following:

• [ ] Tested my code end-to-end against a live Azure subscription.
• [x] Updated the documentation in the docs folder for the affected changes.
• [x] Written unit tests against the modified code that I have made.
• [x] Updated the release notes with a new entry for this PR.
• [x] Checked the coding standards outlined in the contributions guide and ensured my code adheres to them.

If I haven't completed any of the tasks above, I include the reasons why here:

• I do not currently have access to Azure to test this but I have done so in the past.

Below is a minimal example configuration that includes the new features, which can be used to deploy to Azure:

let myServiceBus = serviceBus {
    name "my-namespace"
    sku (Premium OneUnit)
    add_topics [
        topic {
            name "topicA"
            max_message_size 1024<Kb>
        }
    ]
}

[isaacabraham]

@MartinWa We'll schedule some time in to test this end-to-end and then merge in - looks good in principle. Thank you :-)