DepGraphQuery: correctly skip adding edges with not-yet-added nodes Fixes https://github.com/rust-lang/rust/issues/142152. The current logic already skips some edges, so I'm not sure how critical it is to have *all* the edges recorded, the logic seems to only be used for debug dumping. Recording all edges requires supporting holes in the `LinkedGraph` data structure, to add nodes and edges out of order, https://github.com/rust-lang/rust/pull/151821 implements that at cost of complicating the data structure.