[A11y] ui5-list announces "Contains Deletable Items" when using deleteButton slot for non-delete actions (Move Up/Down)

Bug Description

When using ui5-list with selectionMode="Delete" to render custom row actions (like move up/down buttons)
in the deleteButton slot, screen readers incorrectly announce "Contains Deletable Items" even though
there are no delete buttons present.

Affected Component

UI5-List

Expected Behaviour

The list should not announce "Contains Deletable Items" when the deleteButton slot contains non-delete
actions, or there should be an alternative selectionMode value (e.g., "Actions" or "Custom") that
enables the slot without the misleading ARIA announcement.

No announcement about deletable items, or a configurable announcement

Isolated Example

No response

Steps to Reproduce

1. Create a ui5-list with selectionMode="Delete"
2. Add ui5-li items with ui5-button elements in the deleteButton slot using move icons
   (arrow-top/arrow-bottom)
3. Enable a screen reader (VoiceOver, NVDA, or JAWS)
4. Navigate to the list

Log Output, Stack Trace or Screenshots

  <ui5-list selection-mode="Delete" header-text="Reorder Items">
    <ui5-li>
      Item 1
      <ui5-button slot="deleteButton" icon="arrow-top" accessible-name="Move up"></ui5-button>
      <ui5-button slot="deleteButton" icon="arrow-bottom" accessible-name="Move down"></ui5-button>
    </ui5-li>
  </ui5-list>

### Priority

Medium

### UI5 Web Components Version

2.23.1

### Browser

Chrome

### Operating System

_No response_

### Additional Context

In `List.js`, the `ariaLabelModeText` getter hardcodes the announcement:
  ```javascript
  get ariaLabelModeText() {
    if (this.hasData) {
      if (this.isDelete) {
        return List_1.i18nBundle.getText(ARIA_LABEL_LIST_DELETABLE); // "Contains Deletable Items"
      }
    }
  }

The deleteButton slot is currently the only way to render row-level actions in ui5-li, but using it
requires selectionMode="Delete", which triggers this hardcoded announcement regardless of what actions are
actually in the slot.

WCAG Violations

• WCAG 1.3.1 (Info and Relationships): The announced relationship ("deletable items") doesn't match the
  actual functionality (move actions)
• WCAG 4.1.2 (Name, Role, Value): Screen reader users receive incorrect information about available
  actions

Suggested Solutions

1. Add a new selectionMode value like "Actions" or "Custom" that enables the deleteButton slot
   without the "deletable" ARIA announcement
2. Make ariaLabelModeText configurable via a new prop (e.g., modeAriaLabel) that can override or
   suppress the announcement
3. Add a separate actionsButton slot that doesn't require selectionMode="Delete"

Organization

No response

Declaration

• I’m not disclosing any internal or sensitive information.

Start in List.js at the ariaLabelModeText getter and trace how selectionMode="Delete" and the deleteButton slot produce the list announcement. Confirm with maintainers which proposed API or behavior is intended before changing it. Done means custom row actions no longer cause a misleading "Contains Deletable Items" announcement, with the relevant accessibility behavior covered by tests.