non-focusable widget roles nested within elements with children presentational

[giacomo-petri]

As demonstrated in web-platform-tests/wpt#50045, UA consistently expose non-focusable widget roles nested within elements with children presentational with their implicit role.

For example:

<button>
  Something
  <div role="button">Something</div>
</button>

According to the current specs, the conditional logic does not account for this exception. As written, the nested button should be ignored or treated as a generic element, which does not match existing UA behavior.

Since I'm currently working on Presentational Roles Conflict Resolution in #2237, I'd like to address this discrepancy in that PR. Before doing so, I want to confirm that this is indeed the desired direction.