Add system tests for CEF

[andrewkroh]

What does this PR do?

Add logfile and syslog (udp) system tests for the CEF package.

I removed some duplicate fields from fields.yml files.
And for checkpoint, I converted the checkpoint.event_count field to a long in the JSON.

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all datasets collect metrics or logs.

Related issues

• Relates Add automated tests for security packages #377

Screenshots

--- Test results for package: cef - START ---
╭─────────┬─────────────┬───────────┬───────────┬────────┬───────────────╮
│ PACKAGE │ DATA STREAM │ TEST TYPE │ TEST NAME │ RESULT │  TIME ELAPSED │
├─────────┼─────────────┼───────────┼───────────┼────────┼───────────────┤
│ cef     │ log         │ system    │ logfile   │ PASS   │ 27.426336075s │
│ cef     │ log         │ system    │ syslog    │ PASS   │ 27.180639997s │
╰─────────┴─────────────┴───────────┴───────────┴────────┴───────────────╯
--- Test results for package: cef - END   ---

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

[elasticmachine]

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Build stats

• Build Cause: Pull request #575 updated

• • Start Time: 2021-01-28T20:37:20.033+0000

• Duration: 9 min 42 sec

• Commit: 760f013

Test stats 🧪

Test	Results
Failed	0
Passed	81
Skipped	0
Total	81