[m365_defender] Fix mapping for comments field and add missing fields

[marc-gr]

What does this PR do?

Fixes an incorrect mapping for the comments field and adds missing fields mappings.

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.

[elasticmachine]

Pinging @elastic/security-external-integrations (Team:Security-External Integrations)

[elasticmachine]

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• Start Time: 2022-04-25T12:21:27.585+0000

• Duration: 13 min 19 sec

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Test	Results
Failed	0
Passed	6
Skipped	0
Total	6

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