search: Rename pushResults to setResults

search: Rename pushResults to setResults

pushResults, and the original async search API, were originally intended
so search results that weren't immediate could be added as they come in.
Since then, we've decided that the design of search results is that they
should finish at once with all results. Thus, the code was modified so
that pushResults always overwrote the current result set. As such, it makes
sense to rename the method so that the name matches the behavior.

https://bugzilla.gnome.org/show_bug.cgi?id=693836