bugfix: fix CoreRequestProgressBar jarking problem

[PritamBag]

Describe the Bug

In AppContainerLayout, the CoreRequestProgressBar is used. The issue occurs when the CoreRequestProgressBar is displayed, causing the content of this layout to shift downward. When CoreRequestProgressBar is hidden, the content moves back up, creating a jarring effect. This behaviour should not happen.

To Reproduce

Steps to reproduce the behaviour:

1. Go to http://localhost:3000
2. Click on any menu item from the left sidebar
3. Observe the content shifting up and down when the progress bar appears and disappears(On that page where AppContainerLayout must be used)
4. See the unexpected behaviour (layout content jank)

Expected Behavior

The layout should remain stable when CoreRequestProgressBar appears and disappears. The progress bar should have a z-index to overlay the content without shifting it.

Desktop Environment

• OS: Windows
• Browser: Chrome
• Version: 132.0.6834.160 (Official Build) (64-bit)