[BUG] mgt-file-list popup style issues

[cdragosf]

Describe the bug
mgt-file-list component have overlay problems when popup messages like "Replace file" are shown. Popup content is z-indexed below the main component content.

To Reproduce
It can be tested even in mgt.dev .
Go to this sample: https://mgt.dev/?path=/story/components-mgt-file-list-properties--file-list-upload
Try to upload the same file twice and you'll see the pop-up asking for replace file.
Try to scroll while popup open and see background content, like upload button, file rows separators, etc... in front of the popup.
Styles are broken.

Expected behavior
Popup should be shown in front of anything else.

Screenshots

Environment (please complete the following information):

• OS: Windows 11
• Browser: Chrome and Edge
• Framework: React 17
• Context: SharePoint Framework (but same behaviour in mgt.dev)
• Version: 3.1.3 (4.2.1 has same issue)
• Provider: ...

Additional context
Maybe some z-index will fix this?