Add optional multi-column sorting (primary + secondary) to the table component

[Spark450]

Summary

Add support for multi-column sorting (primary + secondary) in goa-table, enabled via a component property. This should be opt-in so teams can continue using single-column sorting when that meets their requirements.

Reference implementation

multi column sort implemented as desired on this example

UX / interaction requirements

• Single sort (default)
  • Clicking a sortable column header applies that column as the only active sort (current behavior).
• Multi sort (opt-in)
  • Define user interaction to set secondary sort (Click second column header to add/modify secondary sort).
  • Define how to remove secondary sort and revert to single sort
    • 1st click - Sorted (arrow up) - asc
    • 2nd click - Sorted (arrow down) - desc
    • 3rd click - Sort removed

Accessibility considerations

• Sort state must be conveyed to assistive tech.
• keyboard Interaction for setting sort primary and secondary must be maintained.
• Provide clear announcements/labels for primary vs secondary sort state.

Acceptance criteria

• table component has a new property to enable multi-column sorting (primary + secondary).
• Single sort configuration remains supported and documented.
• When multi-sort is enabled:
  • Users can set a primary and a secondary sort (each with asc/desc).
  • Sorting is applied as: primary first, then secondary.
  • UI indicates primary vs secondary sort order and direction.
  • Keyboard interaction supports configuring secondary sort.
  • Sort state is exposed to screen readers appropriately.

[twjeffery]

I have this completed in the initial workspace demo, I just need to pull it out into a new PR to dev