Notebook: embed route bundle debug

Created by: vovakulikov

Based on https://github.com/sourcegraph/sourcegraph/pull/30669

Experimental PR: Do not merge this one anywhere

Basically this PR just moves all notebook deps from the main route (bundle) to the lazy-loaded notebook route where all those deps were used.

Original PR bundle

	This PR bundle size

But still, this embed bundle looks strange. It seems like it has some part from the main App bundle for example - 'react-grid-layout' lib

The screenshot above statoscope shows that the embed bundle has this package included in its bundle. But we know that only Code Insights (which is not in the embed bundle) has this dependency.

My guess is that we use global css styles imports for the react-grid in the SourcegraphWebApp.scss file and this might be a culprit here

It seems like our cache group settings don't work properly if we have more than one bundle entry point (which is the case now when we have embed entry point together with the main app entry point in the webpack config)