VirtualScroller scrolling is jarring when itemSize is changed

[bgoscinski]

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CodeSandbox Case (Bug Reports) https://codesandbox.io/s/zen-shamir-5o79w3?file=/src/VirtualScrollerDemo.vue

Current behavior After a change to itemSize scrolling is jarring.

Expected behavior After a change to itemSize scrolling is smooth.

Minimal reproduction of the problem with instructions

1. Create any VirtualScroller, let it initialize
2. Scroll it, observe scrolling is smooth and scrollbar doesn't jump (good)
3. After VirtualScroller initializes change itemSize binding to different value
4. Scroll it, observe scrolling is jarring - scrollbar jumps back (bad)

What is the motivation / use case for changing the behavior? Good UX

Please tell us about your environment: Windows 10, latest Chrome and Brave

• Vue version: 3.2.31
• PrimeVue version: 3.12.0
• Browser: reproduced on Chrome and Brave, didn't check others

[bgoscinski]

The bug is still reproducible on PrimeVue 3.15.0