Accessibility improvements for role on Table & Column components

[laughnan]

Changes

We're seeing an issue that impacts multiple tables in our application. This is mostly on Windows computers and causes the screenreader to go into a different mode when tabbing into the div (this has role "grid" and the columns have role "gridcell").

• On Windows, role="grid" triggers Application Mode for the Windows screenreader.
  • 90% of screenreader users are on Windows computers (importance of change)
  • Application mode passes all keystrokes to the browser
  • Visitors can no longer "read" the text as they're navigating the Table (which is effectively a grid).
• This does not seem to be an issue on Apple with Voiceover.

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[laughnan]

Creating this PR to support accessibility improvements noted in #1604

[laughnan]

All initial tests in 429a472 pass (without new tests) showing that this change is backwards compatible.

[laughnan]

Component testing

1. Update role prop for Table and Column

2. Confirmation of the UI rendering the right values

[laughnan]

@wuweiweiwu can you give this a review?