Dynamic threads limit

[Support]

When setting the total threads limit, allows to run an unlimited number of tasks (up to the limit of maximum active tasks), while the total number of active threads will not exceed the total limit threads

Example:

• Total threads limit: 1000
• 5 active tasks on 300 threads
• At the start tasks 1, 2, 3 will be launched in 300 threads, 4th in 100 and 5th will be 0 active threads
• According as the queries is complete, active threads will go down one by one:
• 1, 2, 3, left 10 active threads, 4th and 5th will fully work in 300 threads

In this way we can maintain a constant number of active threads