Gallery: Item navigators are permanently disabled

[ekh-anadeainc]

Describe the bug

Item navigators are permanently disabled in the gallery component.

This happens because the GalleriaThumbnails component uses computed properties instead of functions to determine the disabled state, and GalleriaItem still uses functions.

Pull Request Link

#7319

Reproducer

https://primevue.org/galleria/#itemwithouthumbnails

Environment

Any environment

Vue version

3.5.13

PrimeVue version

4.3.0

Node version

20

Browser(s)

No response

Steps to reproduce the behavior

1. Open the official documentation website: https://primevue.org/galleria/#itemwithouthumbnails
2. Try to click on the next or previous button

Expected behavior

Actual behavior: Nothing happens
Expected behavior: The user sees the next/previous image