[8.16](backport #4818) [AWS Firehose] Improve Firehose documentation

[mergify]

Description

Improves AWS Firehose documentation, aligning with the update done on AWS Firehose Integration documentation at elastic/integrations#12732

Further, updates all Firehose related documentations to have the same or similar recommended configurations.

Documentation sets edited in this PR

Check all that apply.

• Stateful (docs/en/observability/*)
• Serverless (docs/en/serverless/*)
• Integrations Developer Guide (docs/en/integrations/*)
• [] None of the above

Related issue

Related : elastic/integrations#12150
Related : #4784

Checklist

• Product/Engineering Review
• Writer Review

Follow-up tasks

Select one.

• This PR does not need to be ported to another doc set because:
  • The concepts in this PR only apply to one doc set (serverless or stateful)
  • The PR contains edits to both doc sets (serverless and stateful)
• This PR needs to be ported to another doc set:
  • Port to stateful docs: <link to PR or tracking issue>
  • Port to serverless docs: <link to PR or tracking issue>

---

This is an automatic backport of pull request #4818 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 9813ea7 has failed:

On branch mergify/bp/8.16/pr-4818
Your branch is up to date with 'origin/8.16'.

You are currently cherry-picking commit 9813ea7c.
  (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:   docs/en/observability/cloud-monitoring/aws/ingest-aws-firehose.asciidoc

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   docs/en/observability/cloud-monitoring/aws/monitor-aws-cloudtrail-firehose.asciidoc
	both modified:   docs/en/observability/cloud-monitoring/aws/monitor-aws-cloudwatch-firehose.asciidoc
	both modified:   docs/en/observability/cloud-monitoring/aws/monitor-aws-firewall-firehose.asciidoc
	both modified:   docs/en/observability/cloud-monitoring/aws/monitor-aws-waf-firehose.asciidoc

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[mergify]

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

[alaudazzi]

LGTM