Step 2C includes controls with value that are directly referenced by labelledby or describedby

[smhigley]

Closes #179, based on discussed resolution

Updates the wording of 2C to specify returning the value text of all controls that allow users to control their value, whether or not they are embedded within a referenced label, or are the referenced label. This is the current real-world behavior of all tested browsers.

I also included controls that are part of an aria-describedby calculation, since in testing FF, Chrome, Edge, and Safari, all browsers implement this in practice as well (ref: https://jsfiddle.net/tfogpnvj/ for a reduced example).

PR tracking

Check these once you have confirmed the related change is not necessary (also add N/A) OR when the relevant issue or PR has been made. Leave uncheck if you are unsure. Read the Process Document or Test Overview for more information.

• [x] Related Core AAM Issue/PR: n/a
• [x] Related AccName Issue/PR: n/a
• [x] Related APG Issue/PR: n/a
• [x] Any other dependent changes? n/a

Implementation tracking

• [x] validator tests n/a
• [x] WPT tests: n/a (not requiring accname test, yet!)
• [x] Browser implementations (link to issue or when done, link to commit):
  • WebKit: n/a, matches current implementation
  • Gecko: n/a, matches current implementation
  • Blink: n/a, matches current implementation
• [x] Does this need AT implementations?

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[spectranaut]

@MelSumner I think this is ready for merge! Not waiting for any dependent changes.

[MelSumner]

@smhigley could you rebase? Once it's green we're ready to merge.

[MelSumner]

👋 @smhigley We'd love to get this rebased for a merge, would you be able to do that?

[MelSumner]

This PR has been moved to the mono repo: https://github.com/w3c/aria/pull/2210