* chore(plugin-server): disrtibute scheduled tasks
Changes I've made here from the original PR:
1. add some logging of task run times
2. add concurrency, except only one task of a plugin will run at a time
3. add a timeout to task run times
This reverts commit 23db43a0dc.
* chore: add timings for scheduled tasks runtime
* chore: add timeouts for scheduled tasks
* chore: clarify duration unit
* chore: deduplicate tasks in a batch, add partition concurrency
* chore: add flag to switch between old and new behaviour
This defaults to new, but can be set to old by setting environment
variable `USE_KAFKA_FOR_SCHEDULED_TASKS=false`
* fix tests
* enable USE_KAFKA_FOR_SCHEDULED_TASKS in tests
