[mongo] collect mongod process cpu percentage for self hosted local mongodb

[lu-zhengda]

What does this PR do?

This PR collects mongod/mongos process cpu usage percent for self-hosted MongoDB that runs on the same host with the agent.

Motivation

https://datadoghq.atlassian.net/browse/DBMON-4604

Additional Notes

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Changelog entries must be created for modifications to shipped code
• Add the qa/skip-qa label if the PR doesn't need to be tested during QA.
• If you need to backport this PR to another branch, you can add the backport/<branch-name> label to the PR and it will automatically open a backport PR once this one is merged

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[codecov]

Codecov Report

Attention: Patch coverage is 82.50000% with 14 lines in your changes missing coverage. Please review.

Project coverage is 89.62%. Comparing base (250b813) to head (f45c8b1).

Additional details and impacted files

Flag	Coverage Δ
activemq	?
cassandra	?
hive	?
hivemq	?
ignite	?
jboss_wildfly	?
kafka	?
mongo	93.26% <82.50%> (-0.26%)	⬇️
presto	?
solr	?

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