Allow queued jobs to be processed by a cron job

[NateWr]

Describe the problem you would like to solve
The job queue introduced in #4622 will be processed automatically in server environments where it is not possible to run cron jobs or service workers. However, some admins will want to process the queue through a cron job.

Describe the solution you'd like
Add support for a single cron job that will process scheduled tasks, as the current cron configuration does, as well as process jobs in the new job queue. Each server should only have to set up one cron job per instance (so one cron job can serve many journals in one installation).

The cron job to process the queue will need to execute more quickly than previous cron jobs, which were typically scheduled ro run hourly or daily. Because this jobs queue will include time-sensitive jobs, the cron configuration should be updated to fire every minute or every thirty seconds.

When migrating from 3.3 to 3.4, existing cron configurations should be considered. We may need to require admins to explicitly opt into the new cron system by modifying their config file, so that we know they have adjusted their cron job to fire at the appropriate intervals.

Who is asking for this feature?
Administrators who want to process the jobs queue from a cron job.

[henriqueramos]

I've create a pull request for OJS and pkp-lib, once they're approved, I will do it for OMP and OPS.

[henriqueramos]

@asmecher Could you please check those pull requests? If they look good enough, I will create the respect ones for OMP/OPS. Thank you!

#7106
OJS

[touhidurabir]

@asmecher all test has passed. PRs

pkp-lib --> #8133
ojs --> pkp/ojs#3476
omp --> pkp/omp#1199
ops --> pkp/ops#348

as per per our last discussion, I have brought back the shutdown function that run one job per web request, change at https://github.com/pkp/pkp-lib/pull/8133/files#diff-d8bccac695c8cacb01f4be531434b57599b8747080dd26b56e8f1cb6d5568274R144-R151 .

[asmecher]

Congratulations, @touhidurabir, I've merged this one!