Scripting: TileLayer.resize() and TileMap.resize() break TileLayer references

Nobody has claimed this yet.

If I call `layer.resize()`, `layer` seems to become disconnected from the TileLayer in the map, and changes I make to it afterwards do not appear in the map. I have to get the layer from the map again in order to be able to make changes.

Similarly, if I call `map.resize()`, then *all* the tile layer references I saved prior to that become unusable, I have to make sure I get the layer references from the map *after* I resize. I am guessing this is because `map.resize()` calls `resize()` on its child layers.

Resizing a layer should not break existing references to that layer. If that can't be avoided, then TileLayer.resize() should at least return the new layer reference (in this case, TileMap.resize() will still wreck layer references, which should be documented).

Use TileLayer.resize() and TileMap.resize() as the entry points and reproduce the reported loss of saved layer references after resizing. Done means existing TileLayer references remain usable after either resize, or the API behavior and any returned replacement reference are clearly established and documented.

Written by the indexing model from the issue text.