Expand docs on the side in the suggest widget

[ramya-rao-a]

First draft for #18582

Features in the PR:

• If either suggestion.details or suggestion.documentation exist, they will appear on the side of the suggest list. If no docs but details match then label, then the docs section is not shown
• To use page up and down in the docs, press ctrl+space and then page up and down as usual
• A logic based on cursor position and viewport length is in place to decide when to swap the list and the docs. Not fool proof yet. Just a starting point

Pending:

• More testing on corner scenarios where the list and docs need to be swapped
• Show docs below when editor window is too small
• A visual cue for when focus is on the docs section vs the list
• Test accessibility and screen reader

Update as of 5/7: Logic to decide when to swap list and docs, where to position the suggest widget and when to re-size the docs is finalized here: https://github.com/Microsoft/vscode/blob/ramyar/docs-on-the-side/src/vs/editor/contrib/suggest/browser/suggestWidget.ts#L817

[mention-bot]

@ramya-rao-a, thanks for your PR! By analyzing the history of the files in this pull request, we identified @joaomoreno and @jrieken to be potential reviewers.

[joaomoreno]

I'll file individual issues for the problems I find.

[joaomoreno]

Code looks OK. I filed a few issues. Nothing blocking in my opinion, just a lot of tweaking. I'll leave the merge decision up to you.

[joaomoreno]

Careful with floats. If all you have is two divs, you should use the usual inline-block display to lay them out side by side.