A per-update predicate inside an edge-level test #2841

We will need to express "the edge is valid among its updates that match a predicate", e.g.
graph.edges[filter.Edge.filter(filter.ExplodedEdge.property("p2") == 4).is_valid()]:
narrow an edge's history to the updates passing an exploded-edge predicate, then ask an edge-level question (is_valid, is_active, a property aggregate) of what is left. Today a term can be scoped by views (Edge.window(..), Edge.layer(..)) but not by a predicate on its own updates. Raised in review of #2643.