fix: Busy button should display wait cursor and have aria-busy

[priscilawebdev]

I was unable to make my cursor appear in my recordings, so unfortunately, there are no before-and-after images.

[TkDodo]

@getsentry/design-engineering I would probably like to streamline the API for busy and disabled a bit. Currently its two booleans, but can you really be in both states? We sometimes set both flags:

sentry/static/app/views/acceptOrganizationInvite/index.tsx

Lines 70 to 71 in 27ba1e6

	busy={isAccepting}
	disabled={isAccepting}

so which cursor you then get depends on how its implemented ...

[JonasBa]

@getsentry/design-engineering I would probably like to streamline the API for busy and disabled a bit. Currently its two booleans, but can you really be in both states? We sometimes set both flags:

sentry/static/app/views/acceptOrganizationInvite/index.tsx

Lines 70 to 71 in 27ba1e6

	busy={isAccepting}
	disabled={isAccepting}

so which cursor you then get depends on how its implemented ...

Let's bring this up to @Jesse-Box. I would like to understand if we can encapsulate busy inside a variant, but I am not sure I understand all the use-cases here.

From what I can tell, busy seems to be very similar to isLoading or something equivalent, and maybe there is something we can do there. Our buttons are very poorly implemented in the sense that they don't really display loading state very well, so maybe we can solve that along with busy.

Aside from that, I think busy is a poorly named prop and an unfamiliar concept in the context of a button, and I suspect that might also be one of the reasons why this might not be used much.