Update the scheduler to use a deployment schedule's max_scheduled_runs if set

[abrookins]

When the scheduler schedules runs, it currently always schedules 10 runs. Now that a deployment schedule will be able to configure the max runs with max_scheduled_runs, the scheduler should use that number if set and fall back to the default of 10.

NOTE: The default should be a constant in the scheduler, not a default value in the schema/DB column.