Restore old findBuildDependencyInQueue behaviour

Dependencies

• [2] TSR3RZC4 Revert "Add a dependency_lookup configuration option to enable (slow) dependency lookup in queue. This behaviour was disabled temporarily in accefbb79 due to slowness in very large queues, but some people might be dependent on it, so it is configurable until the previous behaviour is implemented more efficiently."
• [3] J4AJQ6RX Add a dependency_lookup configuration option to enable (slow) dependency lookup in queue. This behaviour was disabled temporarily in accefbb79 due to slowness in very large queues, but some people might be dependent on it, so it is configurable until the previous behaviour is implemented more efficiently.
• [4] YEXD7CBK Fix findBuildDependencyInQueue
• [5] LSPRR4TK hydra-queue-runner: Disable findBuildDependencyInQueue for now
• [6] WTUBAA5Q hydra-queue-runner: Handle restarted builds whose derivation is gone
• [7] TPSCSZKX Speed up findBuildDependencyInQueue
• [8] OV7F5M3E Merge branch 'queue-17'
• [*] 7YBYT2LQ

Change contents

• edit in src/script/hydra-queue-runner at line 51
  [3.36]→[2.0:26](∅→∅)
  − return undef; # FIXME