Enhance navigation item handling with separate IDs for items

[Adammatthiesen]

This pull request refactors the navigation item configuration for the UI and updates how navigation buttons are created and positioned in the PlateMenu. The main focus is to support separate configuration for "previous" and "next" navigation items, and to adjust their placement in the UI layout.

UI Configuration Changes:

• Added prevNavigationItemId and nextNavigationItemId fields to DisplayItems, replacing the single navigationItemId, to allow different items for previous and next navigation actions.

PlateMenu Logic Updates:

• Updated the getNavItem method to accept a prev boolean and select the appropriate navigation item ID (prevNavigationItemId or nextNavigationItemId).
• Modified the creation of navigation buttons to use the new getNavItem signature, passing true for previous and false for next.

UI Layout Adjustments:

• Changed the slot positions for navigation, back, and clear buttons in the chest template to better align with the new navigation logic and improve UI consistency.