Insights: Add trend button/information on the search result page

Created by: vovakulikov

Part of https://github.com/sourcegraph/sourcegraph/issues/38430

We should add a trend button (FIgma desings) to the search result page. This button should be flagged with experimental feature flag in setting cascade. If the "simple UI" mode is on we should make it clickable and it should open the side panel UI with trends chart (trends chart will be implemented in a seperate issue later)