feature: adjustable semaphore path for the concurrency limits

[fatonramadani]

[MESSAGE_ID=1150792165388202125]

[pcc-huangm]

If this is to allow being able to allow multiple executions of the same script to have concurrency limits set on some sort of key I could use this feature. Eg. perhaps globally you want to allow a user to run 2 "heavy" tasks. So all your heavy scripts would have concurrency: = maximimum number of runs = 2 = per time window = 5 mins