Implement a limit for the number of simultaneous tasks

[Sogolumbo]

Pre-Submission checklist

• There is no existing issue that already asks for this feature.
  
• The feature already exists in rclone (on your PC or in Termux)
• I am prepared to help make this feature

What version of Round Sync are you using (About -> App version)?

2.5.6

What problem are you trying to solve?

I use a NAS (mechanical hard disk drive) as a remote storage which I make daily backups to (transfer of ~10GB per day). There are several tasks which are part of the backup. If the tasks run simultaneously, the total transfer bandwidth drops very significantly:
Single Task: ~8MB/s
3 Tasks: ~200KB/s
This performance dropoff is so strong that it increases transfer duration to an insufferably long time.
It's quite likely that the bottleneck is the hard disk drive attached to the NAS, but I'm not sure about that.

What should Round Sync be able to do differently to help with this problem?

Implement a maximum amount of tasks running simultaneously, which can be configured in the settings.
I'm not sure if the maximum should be enforced per remote or for all tasks running. In my case the result would be the same since I'm only using one remote.
The other tasks should be put in a queue.

Current workaround

Schedule the individual tasks for different times of day and hope that they don't take too long and overlap.