Implement basic analytics for search history usage

Created by: quinnkeast

Background

We're experimenting with a new way of surfacing search history in the search input itself, as an autocomplete item.

To help us understand beyond internal dogfood feedback if this is a generally effective moment to surface search history, we'd like to make sure interactions with search history items are tracked.

On the old "recent searches" panel on the search home, clicks on recent searches were logged under RecentSearchesPanelSearchClicked. We don't currently have an equivalent for the search history items as autocomplete suggetsions.

Proposal

Likely the most effective action here for analytics to both give us actionable data while protecting privacy is to track when an autocomplete item is clicked – e.g. SearchHistoryAutcompleteSuggestionClicked – without capturing any other data except perhaps the list position of the item out of how many in the set. The latter may tell us how far back folks are going in their history.

@fkling mentioned:

Integrating telemetry with codemirror suggestions is possible but it is not necessarily straightforward.

This will take some investigation to determine feasibility.

/cc @benvenker @lguychard