Remove eval_always from check_private_in_public. This PR attempts to avoid re-computing `check_private_in_public` query. First by marking the query as non-`eval_always`, and by reducing the amount of accesses to HIR as much as possible. Latest perf https://github.com/rust-lang/rust/pull/116316#issuecomment-3094672105 shows that we manage it. The cost is extra dep-graph bookkeeping.