Improve PathFinder/TargetedMovementGenerator

[Stoabrogga]

🍰 Pullrequest

1. Ensure that the Z coordinates of the calculated path are correct. This is similar to what Cmangos and Trinitycore do:
   https://github.com/cmangos/mangos-classic/blob/e593dbcde632ffc4ba04e82ffc01a51695d578a8/src/game/MotionGenerators/PathFinder.cpp#L983
   https://github.com/TrinityCore/TrinityCore/blob/7f5790db6701a46b06b2c3319c3776c1fb93e3d5/src/server/game/Movement/PathGenerator.cpp#L596
2. Improve TargetedMovementGenerator for following pets
3. Fix TerrainInfo::GetWaterOrGroundLevel (can create values below ground level)
4. Remove unused variable in MoveSplineInit.cpp

Proof

see #2726

Issues

fixes #2726

How2Test

Run around with warlock or hunter pets.

Todo / Checklist

none

[ratkosrb]

Does this work correctly for flying and swimming mobs?

[ShiyoKozuki]

Does this work correctly for flying and swimming mobs?

Not sure if this is related but...
On classic, mobs "run away in fear" and will path into water and swim away (if they started on land before running away).
On vmangos, they will never path into water/swim when "run away in fearing"ing (if they started on land before running away).

[Stoabrogga]

Does this work correctly for flying and swimming mobs?

Flying or swimming creatures do not use pathfinding at all, they use shortcuts (2 point paths) and unlike Cmangos and TC I intentionally omitted the z correction there because it should only apply to calculated paths.

@ShiyoKozuki This is not related, you should open an issue if the creature behavior is wrong.

[Stoabrogga]

Added a few other fixes concerning #2726, see first comment.