search: make lucky generator return autoQuery type

Created by: rvantonder

Stacked on https://github.com/sourcegraph/sourcegraph/pull/38354.

This makes the query generator return a new type

type autoQuery struct {
	description string
	query       query.Basic
}

instead of jobs. This to avoid propagating notification values/descriptions to jobs by the generator.

The test output changes to print this struct rather than serialized jobs, which is a bit smaller.

Test plan

Updated tests