Single z-index for tooltips and popups

[ThetaDR]

Override zIndex for cases the popup opens from tooltip (ex.: comments)

[aonnikov]

to be honest, I don't like this approach. It is good as a temporary solution, but eventually overrides will produce more mess because we will have to manually manage all z-indexes.

Ideally, we need to get rid of library that is used in editor for popups and replace them with our popups. Alternatively, we can expose z-index counter or methods for accessing it and use it in text editor.

[haiodo]

I think we need unified z-layer order allocator between popups and tooltips.

[haiodo]

Or unify them under one place.

[ThetaDR]

Discussed with @aonnikov, going to use svelte use directive for it, it should make it more stable so it should prevent some of the bugs compared to this approach