Chest, weather, crash, and miscellaneous fixes (#5215)

* Alpha-sort cChestEntity

* Chests: use SendUpdateBlockEntity

* Pathfinder: fix out of range Y

* 1.13: correct weather packet ID

* Chests: fix neighbour scanner

+ Add OnAddToWorld and overload to scan neighbours there, instead of in the constructor/OnUse. This fixes hoppers accessing newly loaded double chests and seeing a null m_Neighbour, thus thinking its a single chest.
* Fix typo in cross coords computation.
* Simplify hopper logic.

* Block entities: ASSERT that type is correct

If you match the block type first before calling DoWithBlockEntity, the corresponding block entity must either be empty or correspond to the block type.

* Chunk: fix some forgotten PendingSendBE cleanup

+ Add cleanup in SetAllData, WriteBlockArea
- Remove RemoveBlockEntity (used once), HasBlockEntity (not used)

* Replace MakeIndex with MakeIndexNoCheck

* Remove extraneous MarkDirty in hopper & chests

src/Mobs/PathFinder.cpp

@@ -192,7 +192,7 @@ bool cPathFinder::EnsureProperPoint(Vector3d & a_Vector, cChunk & a_Chunk)
 	// This fixes the player leaning issue.
 	// If that failed, we instead go down to the lowest air block.
 	int YBelowUs = FloorC(a_Vector.y) - 1;
-	if (YBelowUs < 0)
+	if (!cChunkDef::IsValidHeight(YBelowUs))
 	{
 		return false;