[Search service] Use outside application context

[lukasolson]

We need to create a way to use the new search services outside of the application context (something probably registered inside the start lifecycle of the data plugin).

From #46742 (comment):

a demo of how can i use it in my plugin would be nice (so a plugin that does not register an application)

[elasticmachine]

Pinging @elastic/kibana-app-arch (Team:AppArch)

[lukasolson]

This was actually resolved by #57448. The search function is now exposed in the data plugin search service start contract:

const [coreStart, depsStart] = await core.getStartServices();
const response = await depsStart.data.search.search(request, options).toPromise();