[EPIC] Pathfinding, movements, leashing and more

[Yehonal]

I'm starting this discussion to gather as much information as possible regarding the issues we've been facing with the entire movement system.

This is currently one of the most noticeable problems affecting the in-game quality of life, and we aim to address all the criticisms surrounding this topic.

Related issues

From AzerothCore

• Some mobs dont follow los behaviour #22096
• Los Problem with Multiple Npcs. #19697

From ChromieCraft

• [Mobs resetting] Mobs not properly aggroing and they reset in middle of aggro range chromiecraft/chromiecraft#7345
• Open world caster mobs will not reposition when breaking LOS, stay aggro and wander at current location. chromiecraft/chromiecraft#8201
• Bristleback Geomancer Pathing Bug chromiecraft/chromiecraft#7294 (comment)

Possible critical PRs

• fix(Core/AI): Improve creature leashing behavior. #19751
• More movement-related PRs: https://github.com/azerothcore/azerothcore-wotlk/pulls?q=is%3Apr+is%3Aclosed+movement+label%3Afile-cpp

[blinkysc]

The biggest discriminator I have noticed is it's always a SmartAI enabled creature with movement issues. I thought it was limited to casters but also maybe melee too and tried to address it with this. However, while this seems to fix the issue, it seems the longer the server runs (maybe a few hours+) the more apparent the issue re appears.