Adding details about retrieving CycloneDX SBOMs in Console

[SharpRake]

Type of change

Documentation update

Update docs for the Console's image SBOM tab to reflect current UI and functionality.

What should this PR do?

resolves https://github.com/chainguard-dev/internal/issues/5689

Why are we making this change?

The Console's SBOM tab has been updated — it now has six columns (adding Type and Subpath), a Download button with a drop-down to choose between SPDX and CycloneDX formats, and two drop-down menus instead of one. The existing docs were out of date and referenced outdated screenshots.

What are the acceptance criteria?

• The Images Directory doc accurately describes the six-column SBOM table
• The Retrieve Image SBOMs doc correctly describes how to download SBOMs in both SPDX and CycloneDX formats from the Console
• Screenshots reflect the current Console UI

How should this PR be tested?

1. Navigate to the updated pages in the deploy preview
   • Using the Chainguard Console
   • How to Retrieve SBOMs and attestations for Chainguard Containers
2. Verify the SBOM tab description matches the current Console UI (six columns, two drop-downs, Download button with format options)
3. Confirm the new screenshot shows the nginx SBOM tab with the Download drop-down visible

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[matthewhelmke]

It looks like the column headings and data have changed.

[matthewhelmke]

LGTM, thanks!