This is a change in search result behavior in that location
information is no longer provided by default with search results.
Although this looks like a wide-ranging change, it's mostly a
mechanical replacement of the explain bool flag with a new
search.SearcherOptions struct, which holds both the Explain bool flag
and the IncludeTermVectors bool flag.
This commit reverts a previous optimization attempt 3f588cd4a that
tried to trim or shrink the array of child searchers in a
search-disjunction.
Although I am not sure why at the moment, that optimization
incorrectly broke higher level boolean queries, but reverting so that
functionality is restored.
Disjunction searchers are used heavily by higher-level searchers, like
prefix searchers. In that case, a disjunction searcher might have
many thousands of child searchers.
This commit adds an optimization to close each child term searcher as
soon as a child searcher is finished and remove it from the
disjunction searcher's children.
