[7.17](backport #42442) x-pack/filebeat/input/httpjson: add metrics for number of events and pages published

[mergify]

Proposed commit message

This is intended to match the events and batches published by the CEL input, but there is no concept of batches in HTTPJSON, the nearest being paging.

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 httpjson: add event publishing metrics #42340

Use cases

Screenshots

Logs

---

This is an automatic backport of pull request #42442 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 71900c4 has failed:

On branch mergify/bp/7.17/pr-42442
Your branch is up to date with 'origin/7.17'.

You are currently cherry-picking commit 71900c4d8.
  (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/rm <file>..." as appropriate to mark resolution)
	both modified:   x-pack/filebeat/docs/inputs/input-httpjson.asciidoc
	both modified:   x-pack/filebeat/input/httpjson/input.go
	deleted by us:   x-pack/filebeat/input/httpjson/metrics.go
	deleted by us:   x-pack/filebeat/input/httpjson/request.go
	deleted by us:   x-pack/filebeat/input/httpjson/request_test.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]

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