feat(ui5-color-picker): add accessibleName property for unique landmarks

[hinzzx]

Overview

Currently with our ui5-color-picker if multiple color picker instances on a page all have the same "Color Picker" label for their role="group" landmark, violating WCAG 2.2 requirement that landmarks must have unique role/label combinations

Solutions

1. Added accessibleName property:
2. Changed template's html wrapper from section to div

• Why this matters:
  • <section> is a semantic landmark element (like <nav>, <main>, <aside>)
  • HTML landmarks are automatically exposed to assistive technologies
  • Using <section> with role="group" creates conflicting semantics
  • <div> with role="group" is the correct, non-landmark approach
  • ARIA groups are meant for related form controls, not page sections
  • This prevents the color picker from being announced as a navigable landmark

[ui5-webcomponents-bot]

🧹 Preview deployment cleaned up: https://pr-12968--ui5-webcomponents.netlify.app

[unazko]

I've tested the accessibleName and accessibleNameRef APIs and they work as expected.

• When accessibleNameRef and accessibleName are provided then accessibleNameRef would take priority
• accessibleNameRef properly applied when used stand alone
• accessibleName properly applied when used stand alone

Also the code looks clean.