[C++][AzerothCore] Flightmaster's Whistle for AzerothCore (allows teleport to nearest flight master in current area)

[silviu20092]

Flightmaster's Whistle for AzerothCore (allows teleport to nearest flight master in current area) - this was actually a system implemented by Blizzard starting with Legion expansion.
Github repo: https://github.com/silviu20092/mod-flightmaster-whistle