Prevent context menu "jumping" when swapping between loading state and items due to scrollbars

Issue

When the Duo Chat context item selection menu switches between the loading state, and a list of context items which cause scrollbars to show, the whole menu "jumps". This is a bit jarring when typing as the loading state / items switch back and forward rapidly.

This issue can be seen here:

To reproduce

Follow these testing steps to enable the context feature gitlab#488352 (comment 2118028680)

Open a repository with enough files to cause scrolling when searching

Open Duo Chat, type /include -> Files and type to search to trigger the issue

Proposed solution

Improve layout so we don't get a "jump` when the scrollbar pops in and out

Investigate if the current debounce time should be increased