[Filebeat] httplog - reduce duplication to shrink log message size

[andrewkroh]

Proposed commit message

The request and response bodies are included twice in request tracer messages. The body appears in both the event.original and http.{request,response}.body.content. This removes the body from the event.original. It should help reduce the log message sizes for large responses.

The motivation is to allow larger responses to fit into the request tracer log. When a log message exceeds the max size of a log (default 1 MiB) then the message is dropped and a warning is logged by zap to stderr.

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.

[elasticmachine]

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

[mergify]

This pull request does not have a backport label.
If this is a bug or security fix, could you label this PR @andrewkroh? 🙏.
For such, you'll need to label your PR with:

• The upcoming major version of the Elastic Stack
• The upcoming minor version of the Elastic Stack (if you're not pushing a breaking change)

To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v8./d.0 is the label to automatically backport to the 8./d branch. /d is the digit

[elasticmachine]

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• Start Time: 2023-09-07T11:20:00.530+0000

• Duration: 74 min 47 sec

Test stats 🧪

Test	Results
Failed	0
Passed	3177
Skipped	174
Total	3351

💚 Flaky test report

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[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b feature/fb/httplog-no-body-in-event-original upstream/feature/fb/httplog-no-body-in-event-original
git merge upstream/main
git push upstream feature/fb/httplog-no-body-in-event-original