search: use minimal search arguments

Created by: rvantonder

This removes the dependency on args search.TextParameters from the point at which we create search jobs. It means our toplevel search functions take a 3-tuple of just the list of jobs, search.RepoOptions, and the timeout value. Compare this to the massive footprint of TextParameters previously, tracking much state that is irrelevant to the now search jobs.

There's opportunity to merge some of the above toplevel functions so we don't have to keep propagating this 3-tuple. Will do some of that in a follow up. See inline for more comments.

The build should pass, if it doesn't it's probably a flake, so I'm putting it up for review before it's green.