feat(ui5-color-palette-item): introduce selected state

[hinzzx]

We are introducing a selected property to the ui5-color-palette-item. This enhancement allows users to explicitly set a selected state to any ui5-color-palette-item.

For example, previously the first item was always on focus when opening the ui5-color-palette-popover.

Additionally, when one item is selected, any previously selected item will be deselected, ensuring that only one item can be selected within a ui5-color-palette at any given time.

The selected state could be set either by:

• Setting it explicitly by using the selected property;
• By clicking on a <ui5-color-palette-item> with the mouse;
• By pressing Enter or Space upon focused <ui5-color-palette-item>;

[unazko]

The focus border is still 1px in high contrast themes and it should be 2px. The swatches in the mobile view could get cut on Galaxy Fold device: On all other device simulations the display is good. Apart from that the change seems good to me.

[hinzzx]

The swatches in the mobile view could get cut on Galaxy Fold device

The misalignment on Galaxy Fold is not introduced by the change