Pass all default search modal view links from backend

From !128376 (comment 1499446007):

[t]he information for the default search options will be being pulled from three different sources:

• localStorage (for the frequent projects/groups)
• data parsed from the page (for the "persistent" links (i.e., this context_switcher_links method))
• Vuex store derived links (for the context-specific issue/MR links)

This is messy and convoluted. Once https://gitlab.com/gitlab-org/gitlab/-/issues/411879 is done, the backend will have all the information it needs for all of these, at request time, to determine which links should be rendered.

In a future iteration, it'd be nice if the frontend just rendered the links provided by the backend, and nothing else. That would allow us to remove the localStorage implementation and the Vuex store.

The goal of this would be to make the frontend implementation much neater: it'd simply render the data given to it from one location.