Tour: add structural search step using query param
Created by: attfarhan
Adds an additional step to the tour that explains structural search. This gets displayed if the search results page URL has an onboardingTour
query param appended to it, and the search conducted was a structural search.
The query param gets appended to the results page URL whenever the tour is active. If users click our structural search example in the tour, we will enable the structural search toggle. Therefore, when users click our structural search example in the tour, we'll display this additional tour tooltip.
This PR is based off of the existing PR https://github.com/sourcegraph/sourcegraph/pull/12972.