Implement System Tests for Live Viewer

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The Live Viewer in Mantid Imaging is an essential tool that currently lacks dedicated system tests. To ensure its reliability and performance, system tests need to be created to validate its functionality during real-time data visualization.

Desired Behaviour
The Live Viewer should function smoothly and reliably, displaying real-time data without errors

Current Behaviour
There are no dedicated system tests for the Live Viewer, which could lead to undetected issues affecting its real-time data capabilities.