feat(search): more search improvements

[thmsobrmlr]

Problem

The search had some problems... see below.

Changes

This PR:

• allows filtering search results by entity type (i.e. insight, dashboard, ...), so that when you click on a tab only results for that tab will be loaded. this is necessary as the limit in the query applies to all results and there might not be any or just very few results for a given tab otherwise.
• allows selecting extra_fields by entity. this is necessary to show alternative name fields like derived_name for insights.
• allows searching a weighted set of search_fields. this is necessary to search alternative names like title for notebooks or key for feature flags. this means we can also search descriptions with a lesser weight.
• adds a basic preview to search results

How did you test this code?

Added tests & clicked around

[github-actions]

Size Change: -14.9 kB (-1%)

Total Size: 1.99 MB

Filename	Size	Change
frontend/dist/toolbar.js	1.99 MB	-14.9 kB (-1%)

_{compressed-size-action}

[Twixes]

Love search now, the results seem pretty good.
As you may notice, I pushed a small change to make skeleton sizing joy-sparking. One visual bug I noticed: in one spot we're using bg-bg-3000-light, which seems pretty wrong, because that's the light mode version being hard-coded. Should be bg-bg-3000. Just pushed a fix.
The whole command bar is also in a dire need of hover/focus states, it's pretty hard to use otherwise. So I'm gonna give the green check now, but we that's one improvement we've got to make before rolling this out.

[Twixes]

Had to add this as ESLint was complaining about issues due to our Cypress code not being properly typed

[Twixes]

shadow amounts to a border-bottom in 3000 mode, which makes sense for buttons, but does not look great here IMO. Are we getting rid of the modal shadow in 3000 completely @corywatilo?