DBP: Add sleep duration on pixels

[jotaemepereira]

Task/Issue URL: https://app.asana.com/0/1199230911884351/1207278682082256/f
Tech Design URL:
CC:

Description:
Creates a sleep observer that checks for each scan being run when the computer goest to sleep and calculates that time. Then the time that computer has been set to sleep is added as a parameter in the site and post site loading pixels.

Steps to test this PR:
This is not easy to test; I recommend doing the following because the timing of the sleep matters.

Add the following function to the ScanOperation and import IOKit. Then call the putComputerToSleep when the task starts after line 82.

func putComputerToSleep() {
        let task = Process()
        task.launchPath = "/usr/bin/pmset"
        task.arguments = ["sleepnow"]

        let pipe = Pipe()
        task.standardOutput = pipe
        task.launch()
        task.waitUntilExit()
    }

• Start PIR from scratch and use a profile with many profile queries (two names and two addresses are okay).
• Make sure you attach the debugger on Xcode to the background agent
• Then, when the initial scans start, the computer will setup to sleep automatically.
• Wait 10 minutes
• Come back and kill the agent from the terminal (to avoid putting your sleep again), you should have this command in hand.
• Check the logs on Xcode, you should see the sleep duration set in some of the brokers, you can also check the SleepObserver logs with some information.