Cherry-pick #20391 to 7.x: Add host inventory metrics to googlecloud compute metricset

[kaiyan-sheng]

Cherry-pick of PR #20391 to 7.x branch. Original message:

What does this PR do?

Why is it important?

This PR is to add proposed host common fields into compute metricset:

• host.id
• host.name
• host.cpu.pct
• host.network.in.bytes
• host.network.in.packets
• host.network.out.bytes
• host.network.out.packets
• host.disk.read.bytes
• host.disk.write.bytes

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.

How to test this PR locally

1. Start Metricbeat googlecloud module: ./metricbeat modules enable googlecloud
2. Edit modules.d/googlecloud.yml to only include compute metricset:

- module: googlecloud
  metricsets:
    - compute
  region: "us-east1"
  project_id: elastic-observability
  credentials_file_path: "/Users/kaiyansheng/Downloads/elastic-observability-d17781618202.json"
  exclude_labels: false
  period: 300s

3.Change add_host_metadata processor config in metricbeat.yml file:

processors:
  - add_host_metadata:
      replace_fields: false

4. Start metricbeat
5. You should see metrics from compute metricset and includes fields listed above.

[elasticmachine]

Pinging @elastic/integrations-platforms (Team:Platforms)

[elasticmachine]

💚 Build Succeeded

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Build stats

• Build Cause: [Pull request #20724 updated]

• Start Time: 2020-08-21T13:56:55.681+0000

• Duration: 54 min 18 sec

Test stats 🧪

Test	Results
Failed	0
Passed	843
Skipped	72
Total	915