Add tests for `readonly` switch keyboard events

[chrisdholt]

This issue exists to track the addition of keyboard events for readonly switch scenarios with the fix to #6304. This fix is being made async with a migration over to playwright which complicates getting that PR completed or risks losing the newly added tests given a significant migration including the addition of new tests.

Once the playwright conversion is complete, this issue can be taken up and tests can be added for ensuring that enter/space does not fire an event when the control is in readonly mode.