Adjust random movement wait time and implement variable wait times

This makes creature random movement behave like it does on retail where there's a 50% chance the creature will wait between 5 - 10 seconds when reaching a point or alternatively move to the next random point almost instantly.

Here's a video showcasing how it works on retail (compared to MaNGOS, but it still just as relevant to TrinityCore as well): https://www.youtube.com/watch?v=HSEGkMIRZZU