fix: Prevent ariaLabel on code editor from conflicting with ace's built-in aria-label

[avinashbot]

Description

We're overriding ace's built-in aria-label by using our own aria-labelledby, which is a property not touched by ace. Ace's built-in aria-label provides cursor information, so we need to fetch and include that information ourselves. After consulation, using aria-describedby to provide the label has been ruled out, so we have to go with this approach. A number of other alternatives (using setMessages, using the groupAriaLabel instead of the textarea, etc.) have also been ruled out.

Important: The strings are being translated now, and they'll be included in a separate PR, but merged at this same time as this one.

Related links, issue #, if available: AWSUI-24619

API changes

• New i18nStrings property for code editor: cursorPositionAriaLabel
  • Expected usage: cursorPositionAriaLabel: row => 'Cursor at row ' + row
  • This string is combined with the ariaLabel.
  • The idea is that we release with I18nProvider support from the very beginning, so it's a no-touch upgrade for all internationalization users, and even if they don't, having a working ariaLabel is a better alternative than just getting just the cursor position (but obviously, both would be great).

How has this been tested?

Updated relevant tests.

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.34%. Comparing base (0a7c2fe) to head (6403531). Report is 36 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2123      +/-   ##
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+ Coverage   95.16%   95.34%   +0.17%     
==========================================
  Files         685      687       +2     
  Lines       18350    18386      +36     
  Branches     6124     6153      +29     
==========================================
+ Hits        17463    17530      +67     
+ Misses        828      802      -26     
+ Partials       59       54       -5     

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[avinashbot]

Superceded by #2282