[8.x](backport #40968) Restore docker.network.in.* and docker.network.out.* fields in docker module

[mergify]

Proposed commit message

• WHAT: Restore docker.network.in.* and docker.network.out.* fields in docker module
• WHY: These fields contain network incoming and outgoing stats per seconds and should not have been deprecated
  in favour of docker.network.inbound and docker.network.outbound which contain network stats since the container started.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Disruptive User Impact

Author's Checklist

• [ ]

How to test this PR locally

1. Package metricbeat for docker PLATFORMS=linux/arm64 PACKAGES=docker mage package
2. Bring up elastic-stack elastic-package stack up -d -v --version 9.0.0-SNAPSHOT
3. In a machine (VM or local) with docker installed run Metricbeat by:

docker run -d \                                                                             
  --name=metricbeat \ 
  --user=root \
  --volume="$(pwd)/metricbeat.docker.yml:/usr/share/metricbeat/metricbeat.yml:ro" \
  --volume="/var/run/docker.sock:/var/run/docker.sock:ro" \
  --volume="/sys/fs/cgroup:/hostfs/sys/fs/cgroup:ro" \
  --volume="/proc:/hostfs/proc:ro" \
  --volume="/:/hostfs:ro" \
  docker.elastic.co/beats/metricbeat-oss:9.0.0 metricbeat -e \
  -E output.elasticsearch.hosts=["https://elasticsearch:9200"] -E output.elasticsearch.ssl.verification_mode=none -E  output.elasticsearch.username=elastic -E output.elasticsearch.password=changeme

4. Explore the docker.network.in.* and docker.network.out.* in Kibana discover

Related issues

Screenshots

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This is an automatic backport of pull request #40968 done by [Mergify](https://mergify.com).

[elasticmachine]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)