Expose cronWorkflowWorkers as config item.

[sarabala1979]

Summary

Currently `cronWorkflowWorkers' was hardcoded. In some scenarios, if the user is using cron workflow heavily, they need more workers to process the cronworkflow.

What change needs making?

Use Cases

When would you use this?

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[tooptoop4]

does it mean if I have 9 different cronworkflows set to run hourly that one will be missed?

[agilgur5]

Added in #11457 (albeit as an argument, not a config option)

[agilgur5]

does it mean if I have 9 different cronworkflows set to run hourly that one will be missed?

I believe it's more that there are 8 (lightweight) threads running by default. So if you have 9 cron schedules trigger simultaneously, they all get added to the queue and up to 8 can be processed in parallel (also depends on number of cores and other things running on the CPU etc).
A CronWorkflow primarily creates Workflows, so I'd imagine all 8 could be processed in less than a second, and then the 9th gets processed by the first thread that opens up.

@sarabala1979 feel free to correct me as you obviously know this code better than me!

[agilgur5]

(^that is also given a single controller instance without any sharding)