What does "svc power stayon wireless" do?
Executing svc power on the shell will bring the usage:

usage: svc power stayon [true|false|usb|ac|wireless]
         Set the 'keep awake while plugged in' setting.


The command will set whether to keep your device awake (prevent sleeping) or not while it's being charged on specific platform: USB charging, AC power, wireless charging, or all of them:


true will set all flags (usb, ac, wireless)
false will clear all flags
usb/ac/wireless will set that specific flag while clear the other


The same setting usually can be accessed on "Developer options" named "Stay awake", though it's simpler with only toggle to turn on/off.

Reference: source code of com.android.commands.svc.PowerCommand