Cleanups for embedded Jaeger

[doppleware]

1. Fonts should be smaller and aligned with vscode font sizes (which would be available as CSS variables)
2. Implement a selection indication so that if the open side pane is of a specific span that span will be selected in the jaeger (selection indication and toggled). If there are multiple matches, use the first match or the currently selected one if it matches)
3. Change the 'code' marker to an 'insight' marker (TBD which icon). Use that marker to allow the user to change the side pane according to the selected span, without code navigation. Notice that leaving the Jaeger window or closing it should refresh the sidepane to the correct one based on the code position.