Squashed: grid-entity-integration partial features for 7DRL 2025 deployment

This squash commit includes changes from April 21st through 28th, 2024, and the past 3 days of work at 7DRL.
Rather than resume my feature branch work, I made minor changes to safe the C++ functionality and wrote workarounds in Python.

I'm very likely to delete this commit from history by rolling master back to the previous commit, and squash merging a finished feature branch.

src/UIDrawable.h

@@ -28,7 +28,8 @@ class UIDrawable
 {
 public:
     void render();
-    virtual void render(sf::Vector2f) = 0;
+    //virtual void render(sf::Vector2f) = 0;
+    virtual void render(sf::Vector2f, sf::RenderTarget&) = 0;
     virtual PyObjectsEnum derived_type() = 0;
 
     // Mouse input handling - callable object, methods to find event's destination