Shadow DOM prevents ion-fab-button's native button from participating
in form submission. Port the hidden-button pattern from ion-button:
inject a hidden <button> into the associated form (found via the new
`form` prop or by walking up to the closest <form> ancestor), then
click it on Host click to trigger native form submission and Enter-key
support.
Fixes ionic-team#18550

brandyscarney changed the title fix(fab-button): restore submit, reset, and disabled functionality fix(fab-button): restore submit, reset, and disabled form functionality