refactor(ui5-li, ui5-list): changes accessibleRole type

[yanaminkova]

Changes the type of accessibleRole property for both ui5-li and ui5-list.

BREAKING CHANGE: The accessibleRole property for both ui5-li and ui5-list has been updated from a string type to an enum type.
Additionally, the new enums ListItemAccessibleRole and ListAccessibleRole have been introduced for these properties respectively.
The available options for the ui5-li:
ListItem- Represents the ARIA role "listitem". (by default)
MenuItem - Represents the ARIA role "menuitem".
TreeItem - Represents the ARIA role "treeitem".
Option - Represents the ARIA role "option".
None - Represents the ARIA role "none".

The available options for the ui5-list:
List- Represents the ARIA role "list". (by default)
Menu - Represents the ARIA role "menu".
Tree - Represents the ARIA role "tree".
ListBox - Represents the ARIA role "listbox".
If you have previously used:

<ui5-li accessible-role="menuitem"> List Item</ui5-li>
<ui5-list accessible-role="tree"> List </ui5-list>

Now use:

<ui5-li accessible-role="MenuItem"> List Item</ui5-li>
<ui5-list accessible-role="Tree"> List </ui5-list>

Related to #8461, #7887

[nnaydenow]

Seems related to: #8810 . Lets wait until the other task is completed

Update: Ignore this comment

[nnaydenow]

LGTM