List: key uses array index by default

[edizcelik]

We are currently using testid as the default key prop for each list item. This causes tracking issues if the provided items do not have an id property and if there was no key generator function was provided. I think we should initiate the key variable with undefined and then generate a unique string for it if there is no available id property in the item object or there was no listItemKeyGenerator provided as a prop.
https://github.com/Hipo/react-ui-toolkit/blob/main/src/list/List.tsx#L39

[yasincaliskan]

Solution:

• Keep the initial key variable to undefined
• Generate unique string with https://www.npmjs.com/package/uuid