[system] Add pipeline to rename process.ppid in process data_stream

[andrewkroh]

What does this PR do?

Migrate data from Agent 7.x to ECS 8.0 format.

Agent 7.x produces process.ppid, but in order to comply with ECS 8.0
we want all data to use process.parent.pid.

The process data stream lacked any tests so I added a system test to
verify the pipeline works and validate the fields.yml. I found some
undocumented fields.

Relates #2363 #2512

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• I have verified that Kibana version constraints are current according to guidelines.

Related issues

• Relates ECS 8.0 Meta Issue #2363
• Relates [system] Upgrade ECS to 8.0.0 #2512

References

• 7.x source code producing the process.ppid - https://github.com/elastic/beats/blob/d420ccdaf201e32a524632b5da729522e50257ae/metricbeat/module/system/process/process.go#L124

[elasticmachine]

Pinging @elastic/integrations (Team:Integrations)

[elasticmachine]

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• Start Time: 2022-03-17T09:19:10.086+0000

• Duration: 25 min 3 sec

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Total	270

🤖 GitHub comments

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[andrewkroh]

/test

[elasticmachine]

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

[fearful-symmetry]

Looks fine to me, is this something we also want to change on the agent side?

[andrewkroh]

Looks fine to me, is this something we also want to change on the agent side?

It was changed in 8.0 in Beats (https://github.com/elastic/beats/blob/v8.0.0/metricbeat/module/system/process/process.go#L117-L118). So this ensure that data coming from 7.x Agent's will match.

[efd6]

/test