feat(DataTable): new component [run-chromatic]

[amandac628]

/# 📖 Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

This PR improves Data Table sorting behavior, loading/empty-state handling, and custom styling support, and updates docs/stories/playground to reflect the new behavior.

Summary of changes:

Sorting is now opt-in per header (sorting defaults to false).

• Added default sort example using ariasort on sortable headers.
• Sort controls are disabled when there are no body rows.
• In client mode, cycling sort back to none restores the initial slotted row order.
• Loading state is shown consistently when isLoading is true.
• Added row part exposure on internal table rows:
  1. row
  2. row-header
  3. row-body
• Playground updated with night mode switch and Data Table examples.
• Storybook and component reference docs updated.
• Unit tests expanded for the new sorting/loading behaviors.

✏️ Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

🧪 How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Test A
• Test B

✅ Checklist:

• My code follows the SGDS style guidelines and naming conventions
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• Any dependent changes have been merged and published in downstream modules