[elasticsearch] Always report transport address in node_stats

[miltonhultgren]

In the node_stats metricset we were relying on Metricbeat to populate service.address and then later in the Stack Monitoring UI use that to display the IP of the nodes.

Two problems existed with that approach:

1. Metricbeat will populate service.address with the IP/address of the host it connects to in order to collect the metrics, and if you're using scope: cluster that might be a load balancer or it will just be the address of the single node that gets connected, duplicated for all nodes
2. The address populated will be the HTTP address, not the Elasticsearch transport address, which is what Internal Collection reports (and the variables in the Stack Monitoring UI refer to)

This PR changes so that we manually populate service.address by setting event.Host to the transport IP of the node being reported so that each node reports their unique transport IP.

[mergify]

This pull request does not have a backport label.
If this is a bug or security fix, could you label this PR @miltonhultgren? 🙏.
For such, you'll need to label your PR with:

• The upcoming major version of the Elastic Stack
• The upcoming minor version of the Elastic Stack (if you're not pushing a breaking change)

To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v8./d.0 is the label to automatically backport to the 8./d branch. /d is the digit

[elasticmachine]

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• Start Time: 2023-09-20T13:08:02.504+0000

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