[8.18](backport #45810) x-pack/filebeat/input/httpjson: allow template termination without logging error

[mergify]

Proposed commit message

x-pack/filebeat/input/httpjson: allow template termination without logging error

This adds a terminate helper that can be used to signal that a template
should terminate without an error. The termination can (should) be used
to report the reason for the termination which will be logged at DEBUG
level, but otherwise ignored.

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

• [ ]

How to test this PR locally

Related issues

• Closes [Filebeat] Avoid updating Fleet health status to degraded when HTTPJSON template value evaluation is empty #45664

Use cases

Screenshots

Logs

---

This is an automatic backport of pull request #45810 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of f324f29 has failed:

On branch mergify/bp/8.18/pr-45810
Your branch is up to date with 'origin/8.18'.

You are currently cherry-picking commit f324f295a.
  (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
	modified:   x-pack/filebeat/input/httpjson/request.go
	modified:   x-pack/filebeat/input/httpjson/value_tpl_test.go

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   docs/reference/filebeat/filebeat-input-httpjson.md
	both modified:   x-pack/filebeat/input/httpjson/value_tpl.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

[elasticmachine]

Pinging @elastic/security-service-integrations (Team:Security-Service Integrations)

[leehinman]

@efd6 FYI looks like the backport needs some help

[mergify]

This pull request has not been merged yet. Could you please review and merge it @efd6? 🙏