Rollup merge of #142617 - lcnr:search_graph-3, r=compiler-errors

improve search graph docs, reset `encountered_overflow` between reruns

I think this shouldn't really matter for now. It will be more relevant for my current rework as we otherwise cannot partially reevaluate the root goal in case there has been overflow during the prervious iteration.

r? ````@BoxyUwU````

Author: jhpratt