Handle duplicated inputs in topological sort. And do not add the redundant...

Handle duplicated inputs in topological sort. And do not add the redundant control dependencies. The would result in malfunction of
topological sort as it previously doesn't handle duplicated inputs. For example, say node A has three repeated input ^B, node A
will never get added to queue in topological sort, because the number of ready inputs will always be less
than the number of inputs (B is only counted once).
node {
  name: "A"
    op: "SomeOp"
    input:"^B"
    input:"^B"
    input:"^B"
}

PiperOrigin-RevId: 167045325