Core/Movement: Fix some undermap issues with random movement/fear/blink (#22937)

* Core/Movement:
- Only move to point if there is a path that is not a shortcut (which will make the unit move through terrain)
- Added new function to check if there is a vmap floor without search distance
- Units that can fly, are underground but far above the vmap floor will stay underground (bronze drakes in tanaris)
- Don't remove PATHFIND_SHORTCUT from path type in some cases

* Core/Object: Ignore UpdateAllowedPositionZ for flying units.

- This will make flying units go through mountains instead of going to the top and back to the bottom to reach you.

* Core/Object: Revert some changes and let MovePositionToFirstCollision deal with a position without ground

* Missing groundZ change for objects on transport

* use CanFly instead of IsFlying

(cherry picked from commit 9fcbd8f15d)

src/server/game/Maps/Map.cpp

@@ -2537,12 +2537,9 @@ float Map::GetStaticHeight(PhaseShift const& phaseShift, float x, float y, float
     // find raw .map surface under Z coordinates
     float mapHeight = VMAP_INVALID_HEIGHT_VALUE;
     uint32 terrainMapId = PhasingHandler::GetTerrainMapId(phaseShift, this, x, y);
-    if (GridMap* gmap = GetGrid(terrainMapId, x, y))
-    {
-        float gridHeight = gmap->getHeight(x, y);
-        if (G3D::fuzzyGe(z, gridHeight - GROUND_HEIGHT_TOLERANCE))
-            mapHeight = gridHeight;
-    }
+    float gridHeight = GetGridHeight(phaseShift, x, y);
+    if (G3D::fuzzyGe(z, gridHeight - GROUND_HEIGHT_TOLERANCE))
+        mapHeight = gridHeight;
 
     float vmapHeight = VMAP_INVALID_HEIGHT_VALUE;
     if (checkVMap)
@@ -2564,16 +2561,24 @@ float Map::GetStaticHeight(PhaseShift const& phaseShift, float x, float y, float
             // or if the distance of the vmap height is less the land height distance
             if (vmapHeight > mapHeight || std::fabs(mapHeight - z) > std::fabs(vmapHeight - z))
                 return vmapHeight;
-            else
-                return mapHeight;                           // better use .map surface height
+
+            return mapHeight;                           // better use .map surface height
         }
-        else
-            return vmapHeight;                              // we have only vmapHeight (if have)
+
+        return vmapHeight;                              // we have only vmapHeight (if have)
     }
 
     return mapHeight;                               // explicitly use map data
 }
 
+float Map::GetGridHeight(PhaseShift const& phaseShift, float x, float y)
+{
+    if (GridMap* gmap = GetGrid(PhasingHandler::GetTerrainMapId(phaseShift, this, x, y), x, y))
+        return gmap->getHeight(x, y);
+
+    return VMAP_INVALID_HEIGHT_VALUE;
+}
+
 float Map::GetMinHeight(PhaseShift const& phaseShift, float x, float y)
 {
     if (GridMap const* grid = GetGrid(PhasingHandler::GetTerrainMapId(phaseShift, this, x, y), x, y))