TaskDispatcher: pre-declare the notify_no_such_plugin metric

Dependencies

• [2] I7Q3M7V3 TaskDispatcher: Support re-queueing tasks, and dropping tasks after 100 failures.
• [*] SWXGVPJN hydra-notify: extract runPluginsForEvent to a TaskDispatcher

Change contents

• edit in src/lib/Hydra/TaskDispatcher.pm at line 115
  [2.1562]

  [4.1938]
  + $prometheus->declare(

  + "notify_plugin_no_such_plugin",

  + type => "counter",

  + help => "Number of tasks that have not been processed because the plugin does not exist."

  + );