Should we remove the implicit role from `summary`?

[straker]

The summary element in ARIA 1.2 no longer has an implicit role. However it does note that browsers may still give it an implicit role. We should investigate if we should keep the button role as our implicit role for summary or remove it and leave it as having no implicit role.

[WilcoFiers]

I think it wasn't a button when we put it in either. I'm on the fence about this. I think its easier to understand the summary element as just a button. The only difference I'm aware of from actual role=button elms is that it doesn't have presentational children. We could just add an exception for them to nested-interactive.

It's a fairly involved change. We'd need to rethink how we detect widgets for one. We'd need to make sure these elms aren't ignored by required parent / child rules. We'd need to special case them in the accessible name computation, probably more stuff I'm not thinking of off the top of my head. It's the same reason most input types still get implicit role=textbox, even when HTML AAM says otherwise.

Seems like a lot of work, and I'm not sure it gets us much.