[Feat][Button]: Support icon-only attribute

[Westbrook]

Code of conduct

• I agree to follow this project's code of conduct.

Impacted component(s)

Button

Description of the requested feature

Spectrum CSS recently added support for icon only Buttons, we should add them to SWC.

Mockups or screenshots

Implementation notes or ideas

The spectrum-Button--iconOnly class leveraged in the CSS output should be converted to an icon-only attribute. See documentation for this sort of conversion, here.

If present this attribute should visually suppress the id="label" element that delivers slotted content so that it can still be made available to screen readers.

We'll need to add size, variant, static, and treatment versions of this pattern to the various Storybook entries for Button, and if there was a sensible functional test to include with this addition, that would be great, too.

Follow up work, once v2 of the Overlay API has been shipped, can expand on this pattern to deliver the provided text content in a Tooltip, as outlined in the specification for this pattern.

[najikahalsema]

The icon-only button should display the label for button in a tooltip, according to the Spectrum specification. There are also style differences and functional differences that need to be explored and addressed.