Update: option element mapping table

[scottaohara]

This PR does a few things:

1. Adds text indicating that UAs should calculate the x of y position of options similar to radio buttons (this is what happens now, but was not specified)
2. Re: the above mentioned x of y (aria-posinset / aria-setsize) for options, the radio button text that this was pulled from had a few wording updates to keep consistency.
3. adds UA MAY to comments of option, indicating what could be done to correct for invalid nesting of interactive elements within options (per upcoming customizable select where this scenario could occur)

related to https://github.com/whatwg/html/pull/10586 (among other customizable select prs/issues)

Test, Documentation and Implementation tracking

Once this PR has been reviewed and has consensus from the working group, tests should be written and issues should be opened on browsers. Add N/A and check when not applicable.

• [ ] "author MUST" tests:
• [ ] "user agent MUST" tests:
• [ ] Browser implementations (link to issue or commit):
  • WebKit:
  • Gecko:
  • Blink:
• [ ] Does this need AT implementations?
• [ ] Related APG Issue/PR:
• [ ] MDN Issue/PR:

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[scottaohara]

this PR might also need to include an entry for the option element into the accName steps in html aam... specifically regarding the use of the label attribute if that does something beyond just adding/replacing text of the option.

EDIT: in the open ui call we resolved that the label attribute should continue doing what it does for the current select, and that if an author uses it, it'll take priority in displaying its text, rather than whatever the author uses as the nested content of the option. so:

<option label="i am what is shown as the text content of the option">i do not get displayed</option>

also, might be worth calling out that - at least as far as i recall - option in the current select doesnt' always support aria-label, since the UA presented listbox/options didn't always carry over aria-attributes (again, last i recall this wasn't supported everywhere)