Fix installer pre-check UI layout by using scrollable panel

[divyesh-git22]

This PR refactors the Pre-Install Checks UI to use a scrollable Panel
instead of fixed positioning.
what this change does:

• Prevents UI overflow on smaller screens
• Removes dependency on manual spacing
  No installer logic was changed by myside

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[emtuls]

Thank you for the PR @divyesh-git22!

I am testing the PR on Windows 10 and I did notice some issues that need to be addressed:

1. The Pre-Install Checks window seems to be broken:
   Scroll wheels have been added to the sides, which is a great change! But unfortunately, some other things broke in the process:

• The checkbox we had to ensure users have made a snapshot before continuing seems to be missing.
• The Continue and Cancel boxes seem to be missing.
• The True and False indicators next to each check also seem to be missing.

Your code:

This is how I would expect it to look when fixed:

2. The internet connectivity checks seem to have been removed:

Before (original code):

After (your PR):

3. The package selection window still doesn't include the scroll bars on the sides, which I believe was the main concern from Flare-VM Package Installation Windows UI Issue #737

Your code (note there are no scroll wheels on the sides for lower resolutions):

This is how I would expect it to look when fixed:

[emtuls]

See previous comment!