[8.12](backport #39455) x-pack/filebeat/input/internal/httplog: improve req/resp logging

[mergify]

Proposed commit message

Attempt to log the request and response bodies and other details even when copying the body has been reported to have failed.

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.

Disruptive User Impact

Author's Checklist

• Backporting because this is a visibility hole in support case.

How to test this PR locally

Related issues

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Logs

---

This is an automatic backport of pull request #39455 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 3efb1e8 has failed:

On branch mergify/bp/8.12/pr-39455
Your branch is up to date with 'origin/8.12'.

You are currently cherry-picking commit 3efb1e8612.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   CHANGELOG.next.asciidoc

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   x-pack/filebeat/input/internal/httplog/roundtripper.go

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[botelastic]

This pull request doesn't have a Team:<team> label.

[efd6]

No longer a target.

[elasticmachine]

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