feat: add dev warning for missing field definition labels in attribute-editor

[Who-is-PS]

Description

Adds a console warning via warnOnce when an AttributeEditor field definition is missing a label prop. The label is used as aria-label for the inputs in the column, so omitting it degrades the screen reader experience.

This change helps guide developers toward providing accessible labels without introducing a breaking change (making label required).

Related links, issue #, if available: AWSUI-61432

How has this been tested?

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]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.44%. Comparing base (7d1f303) to head (d121224).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4337   +/-   ##
=======================================
  Coverage   97.44%   97.44%           
=======================================
  Files         897      897           
  Lines       26397    26401    +4     
  Branches     9527     9528    +1     
=======================================
+ Hits        25723    25727    +4     
  Misses        631      631           
  Partials       43       43           

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[cansuaa]

Do we need this line? If you mock '@cloudscape-design/component-toolkit/internal' we shouldn't need this since we are only interested in 'warnOnce'. I'd check how the other warnOnce usages are tested e.g.

components/src/button-dropdown/__tests__/button-dropdown.test.tsx

Lines 16 to 23 in 8093e3f

	jest.mock('@cloudscape-design/component-toolkit/internal', () => ({
	...jest.requireActual('@cloudscape-design/component-toolkit/internal'),
	warnOnce: jest.fn(),
	}));
	afterEach(() => {
	(warnOnce as jest.Mock).mockReset();
	});

[Who-is-PS]

Yeah true, the useContainerQuery mock is unnecessary here. I've switched to mocking @cloudscape-design/component-toolkit/internal with just warnOnce: jest.fn(), matching the pattern in button-dropdown and table. This also lets us drop the consoleWarnSpy entirely since we can assert directly on the warnOnce mock and use mockReset() between tests instead of relying on a separate file for a clean warnOnce cache

[cansuaa]

Could you check why it was being triggered twice before deleting it?

[Who-is-PS]

The warning check runs directly in the render body (not in a useEffect/useMemo), so it fires on every render. The original test had useContainerQuery mocked to return a stable value (['m', () => {}]), which prevented the re-render. When I refactored the test to mock @cloudscape-design/component-toolkit/internal instead of @cloudscape-design/component-toolkit, I lost that useContainerQuery mock — so the real hook runs, resolves the container query asynchronously, and triggers a second render → second warnOnce call.