JobLock option reEnqueue to skip trying job again

[evantahler]

This PR adds a new plugin setting for JobLock to skip re-enqueuing the job if another instance of the job is already being worked on.

const jobs = {
  withReEnqueue: {
    plugins: ["JobLock"],
    pluginOptions: {},  // or the default { JobLock: { reEnqueue: true } },
    perform: async () => {
      return "hi";
    },
  },
  withoutReEnqueue: {
    plugins: ["JobLock"],
    pluginOptions: { JobLock: { reEnqueue: false } },
    perform: async () => {
      return "hi";
    },
  },
};