fix: #3618888 Free the Tab key and give the editors an accessible name

Fixes #3618888.

Three accessibility fixes for the two editable integrations (text editor and field widget); the read-only formatter and filter are unaffected:

• Enable Ace's keyboard-accessibility mode, so Tab moves focus out of the editor and Esc leaves it (WCAG 2.1.2 No Keyboard Trap). Guarded for older Ace builds.
• Carry the field's label to the editor as its accessible name (textInputAriaLabel), so assistive technology names the replacement the same as the field.
• Mark the editor required when the original textarea was.

Verification

On Drupal 11.4.5: the editor reports keyboard accessibility on, and the field label "Body" is carried as the accessible name. eslint PASS.

Checkpoints:

• File an issue
• Addition/Change/Update/Fix
• Testing to ensure no regression
• Automated unit testing coverage
• Automated functional testing coverage
• UX/UI designer responsibilities
• Readability
• Accessibility
• Performance
• Security
• Developer Documentation
• User Guide Documentation
• Reviewed by human
• Code review by maintainers
• Full testing and approval
• Credit contributors
• Review with the product owner
• Release notes snippet
• Release

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