fix(ui5-button): announce accessible name

[unazko]

Issue:

• The badge wasn't announced at all when an accessible-name attribute is provided
  for the ui5-button. The reason behind this behaviour is that the screen reader doesn't
  read the inner text nodes of the root button node when the same has aria-label attribute.

Solution:

• The proper badge description text is placed into the aria-label attribute of the root
  button element. As a result the screen reader won't rely on the inner text content
  for the announcements.
• Additionally the design description is also moved into the aria-label attribute,
  in order to keep a proper announcement order.

Fixes: #11350

[Copilot]

Pull Request Overview

This PR fixes an accessibility issue for the ui5-button by updating how the accessible name and badge description are announced. Key changes include:

• Updating the aria-label generation by combining the accessible name, button type, and badge description.
• Adjusting the aria-description handling to return undefined when empty.
• Modifying the Cypress tests to validate the updated accessibility attributes.

Reviewed Changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 3 comments.

File	Description
packages/main/src/Button.ts	Updates aria-label and badge description generation for improved announcement.
packages/main/cypress/specs/Button.cy.tsx	Updates tests to reflect new accessibility attribute behaviors.

Files not reviewed (1)

• packages/main/src/i18n/messagebundle.properties: Language not supported

Comments suppressed due to low confidence (1)

packages/main/cypress/specs/Button.cy.tsx:332

• Consider adding additional tests for edge cases such as badge values like "0" or unexpected non-numeric texts to ensure that the aria-label formation handles all scenarios robustly.

.should("have.attr", "aria-label", `Download 999+ items`);