feat(ui5-color-palette*): resolve landmark uniqueness and missing dialog label

[hinzzx]

Overview

Currently in our ui5-color-palette all color palette items share the same "Color Palette" label for elements with role="region". The problem is that landmarks should have a unique role or role/label/title combination.

Therole="region" creates a landmark - Landmarks are navigational waypoints that must have unique labels across the entire page

When multiple ui5-color-palette components exist on the same page, they ALL had role="region" with the same label "Color Palette". This caused a WCAG 2.2 AA violation: Multiple landmarks with identical labels confuse screen reader users.

Solutions

1. So, that's why we will now use role="group".

   • It is NOT a landmark - it's a generic grouping role
   • Groups with the same label don't violate WCAG because they're not landmarks
   • Still provides semantic structure but without the uniqueness requirement

2. We also added accessibleName

   • This enables developers to differentiate multiple ColorPalette instances when needed:

<ui5-color-palette accessible-name="Background Color"></ui5-color-palette>
<ui5-color-palette accessible-name="Text Color"></ui5-color-palette>

3. ColorPalettePopover gets automatic label

[ui5-webcomponents-bot]

🚀 Deployed on https://pr-12967--ui5-webcomponents-preview.netlify.app

[unazko]

I've tested the accessibleName and accessibleNameRef APIs and they work as expected.
The code is looks clean like in this PR: #12968