Bump default silent timeout to 2 hours

Dependencies

• [2] 5X6FHW3S hydra-eval-jobs: Fix building against the latest unstable Nix
• [3] DPYJFBXU hydra-eval-jobs: Support meta.license being a list
• [4] HVXL2XUZ
• [5] 5MNUNZWR * Store meta.maintainers.
• [6] ZTQEU5QS Hydra: Add support for maxSilent meta attribute (also already added timeout, but not implemented the actual timeout for the build yet)
• [*] 4N5APGRG * Start of a helper tool to evaluate job expressions efficiently.

Change contents

• replacement in src/c/hydra-eval-jobs.cc at line 144
  [3.1]→[2.1375:1460](∅→∅)
  − xmlAttrs["maxSilent"] = int2String(drv.queryMetaInt("maxSilent", 3600));
  [3.1]

  [3.259]
  + xmlAttrs["maxSilent"] = int2String(drv.queryMetaInt("maxSilent", 7200));