[8.16](backport #4433) [Observability Onboarding] Add AWS Firehose quickstart

[mergify[bot]]

Description

This PR adds a new quickstart for AWS Firehose.

Documentation sets edited in this PR

Check all that apply.

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

Related issue

Closes https://github.com/elastic/kibana/issues/191835

Checklist

• [X] 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: \
  • [X] Port to serverless docs: https://github.com/elastic/observability-docs/issues/4434

    ---

    This is an automatic backport of pull request #4433 done by Mergify.

[github-actions[bot]]

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