[8.x] [8.16] Updates CSPM guides to include agentless option (backport #5863)

[mergify]

Fixes #5606 by updating the CSPM deployment documentation to include the new agentless deployment option. Also fixes #4579 by updating the language about the Role ARN configuration field in the AWS guides.

Previews: Set up CSPM on azure
On GCP
On AWS
CSPM landing page

---

This is an automatic backport of pull request #5863 done by Mergify.

[mergify]

Cherry-pick of 4e0ee5f has failed:

On branch mergify/bp/8.x/pr-5863
Your branch is up to date with 'origin/8.x'.

You are currently cherry-picking commit 4e0ee5f1.
  (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/cloud-native-security/cloud-native-security-index.asciidoc
	modified:   docs/cloud-native-security/cspm-get-started-aws.asciidoc
	modified:   docs/cloud-native-security/cspm-get-started-azure.asciidoc
	modified:   docs/cloud-native-security/cspm-get-started-gcp.asciidoc
	modified:   docs/cloud-native-security/cspm.asciidoc
	new file:   docs/getting-started/agentless-integrations.asciidoc
	modified:   docs/getting-started/index.asciidoc
	new file:   docs/serverless/ingest/agentless-integrations.asciidoc

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   docs/serverless/cloud-native-security/cspm-get-started-azure.asciidoc
	deleted by us:   docs/serverless/cloud-native-security/cspm-get-started-gcp.asciidoc
	deleted by us:   docs/serverless/cloud-native-security/cspm-get-started.asciidoc
	deleted by us:   docs/serverless/cloud-native-security/cspm.asciidoc
	deleted by us:   docs/serverless/index.asciidoc

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

[github-actions]

A documentation preview will be available soon.

• 🔨 Buildkite builds
• 📚 HTML diff
• 📙 Preview page

Request a new doc build by commenting

• Rebuild this PR: run docs-build
• Rebuild this PR and all Elastic docs: run docs-build rebuild

_{run docs-build is much faster than run docs-build rebuild. A rebuild should only be needed in rare situations.}

_{If your PR continues to fail for an unknown reason, the doc build pipeline may be broken. Elastic employees can check the pipeline status here.}