Enable multi-select in the table

[mollykreis]

Pull Request

🤨 Rationale

Adds multi-select support in the table as part of #856

Functionality included in this change:

• Add selection checkboxes to rows, group rows, and table header when multi-select is enabled

Functionality explicitly excluded from this change:

• Angular/Blazor support
• Add labels to selection checkboxes. I've added a note in the table accessibility issue that we need to address this in a similar manner to addressing it for the expand/collapse button on group rows: Address Table accessibility issues #1151
• Add support for multi-selection through CTRL+CLICK and SHIFT+CLICK

👩‍💻 Implementation

• Extend TableRowSelectionMode to include multiple
• Extend TableRowSelectionState to include single
• Add checkboxes to rows, group rows, and table when the selection mode was multiple.
  • I had to wrap the checkboxes in a gridcell because a checkbox isn't an allowable direct child of a row. A button also isn't an allowable direct child of a row, so I made the same change to wrap the existing expand/collapse button on group rows in a gridcell
  • I ran into issues because the change event is fired from the nimble-checkbox when a programmatic change to the value is made. Therefore, I am programmatically controlling the state of the selection checkboxes rather than binding to the checked and indeterminate properties from templates.
• Some of the TanStack selection code does not work the way we need it to, particularly around selection + grouping. Therefore, I've written explicit code to:
  • deselect all children of a group when the group row's selection checkbox becomes unchecked
  • determine the selection state of group rows

🧪 Testing

• Added a number of new unit tests
• Manually tested in storybook
• Extended table matrix tests to include all three selection modes
• Added selection modes to the column stories to enable testing selection with other features such as column sizing and grouping

✅ Checklist

• I have updated the project documentation to reflect my changes or determined no changes are needed.

[jattasNI]

Some initial feedback from playing with Storybook and reviewing about half the files.

[rajsite]

Awesome work 🎉