resolves https://github.com/elastic/kibana/issues/56573
In this PR we create a new task manager limit on the config property
`xpack.task_manager.max_workers` of 100, but only log a deprecation
warning if that property exceeds the limit. We'll enforce the limit
in 8.0.
The rationale is that it's unlikely going to be useful to run with
more than some number of workers, due to the amount of simultaneous
work that would end up happening. In practice, too many workers can
slow things down more than speed them up.
We're setting the limit to 100 for now, but may increase / decrease it
based on further research.