Fix opened-traces context-menu going out of view

[hriday-panchasara]

Adjust z-index of the context menu so that its not blocked by other components:

Screen.Recording.2023-03-16.at.2.42.34.PM.webm

[williamsyang-work]

I think this has to do with the context menu being a part of the theia-trace-extension and rendered inside of the iFrame. The solution is probably more complicated than simply increasing the z-value. Probably more like:

• stopping event propagation
• creating and registering vscode commands and context menu items in the extension's package.json

I'm not sure how b) would be able to detect what file is being clicked on. But I haven't investigated this yet.