Improve a11y on checkbox

[jlemay-godaddy]

Describe the bug:
Right now, we are hidding the <input> with CSS when using checkboxes, and create a fake checkbox with SVG on the ::before element inside the <label>. We are unable to enter the label using the keyboard, and even if we are forcing the tabbing using tabIndex=0 we are not able to toggle the checkbox using the space or enter key.

We should revert this and do something more accessible like in the Twenty-Twenty-One theme.

Also, I haven't tested yet, but I assume we are having the same problem with Radio inputs.