Allow to configure shared thread pool for scheduled consumers

For example if you have many routes that starts from a file endpoint, then they are scheduled consumers, each using its own private thread pool with 1 scheduled thread.

So for example having 30 file routes, means 30 threads. The JDK scheduled thread pool is always a fixed size.

We should allow people to configure a custom thread pool, so they can use a single shared pool, with a number of fixed thread, that is shared among the 30 file consumers.