Add ability to syntax highlight read-only search requests displayed in the app

Created by: lguychard

raised by @limitedmage

Some of the search requests displayed on the repogroup homepage or on the new enterprise homepage are partially highlighted, but this highlighting is hardcoded. Other search requests (like in the "Recent searches" panel) have no highlighting:

https://sourcegraph.com/github.com/sourcegraph/sourcegraph@089083a29336eaacdf7206a91bbd7b5e26b96d32/-/blob/web/src/search/panels/RepositoriesPanel.tsx?subtree=true#L95-98

We should probably have a <HighlightedSearchQuery/> (or similar) component that, given a query string, will rely on the frontend query parser to display it as a fully syntax-highlighted search query, consistent with what is shown in the query input.