Docs: Improve DS with SBOM user doc

What does this MR do?

Update the DS with SBOM user documentation to:

• Explain how this feature works
• List various enablement options

This is particularly relevant as we announce Dependency Scanning support for Cargo, Conda, Cocoapods and Swift in the Dependency Scanning CI template using the new DS analyzer.

I ultimately think we need to extract dependency detection to its own page, or the DS analyzer at least. I've tried to keep it concise and did not follow the same detailed enablement instructions we have on the legacy DS feature page (ADO, pre-configured MR, SEP, manually, CI/CD component)...

Here the recommended enablement approach is via the DS CI template, as we've decided in our rollout strategy and as advertised in the migration guide.

Related issues

Author's checklist

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