Backport of dynamic movement implementation for a batch of zones

Zones that are now using dynamic movement:
- Stranglethorn
- Swamp of Sorrows
- The Hinterlands
- Undercity
- Western Plaguelands
- Ashenvale
- Azshara
- Darkshore
- Desolace
- Dustwallow Marsh
- Felwood
- Feralas
- Stonetalon Mountains

Signed-off-by: Cala <calaftp@free.fr>

Author: X-Savior