[DOCS-3901] Add Logs Cost Attribution doc

[maycmlee]

What does this PR do?

Adds Logs Cost Attribution doc with images.

Motivation

PM request. DOCS-3901.

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Reviewer checklist

• [ ] Review the changed files.
• [ ] Review the URLs listed in the Preview section.
• [ ] Check images for PII
• [ ] Review any mentions of "Contact Datadog support" for internal support documentation.

[github-actions[bot]]

Preview links (active after the build_preview check completes)

New or renamed files

• https://docs-staging.datadoghq.com/may/logs-cost-attribution/logs/faq/logs_cost_attribution

Modified Files

• https://docs-staging.datadoghq.com/may/logs-cost-attribution/logs/faq/

[drichards-87]

@maycmlee I responded to your questions. Everything looked good to me so I went and approved the PR.