editor: setting up the update callbacks for n-slicing

I did some refactoring on image and mesh, where I created a 'deformer' that manages which mesh to show.
I also abstracted out the parts in Mesh that deals with rendering specifically, called MeshDrawable.
There's also a simple UI gated behind a feature flag that shows the N Slicing panel, where you can create, delete, update axis data (hold alt to show the remove axis button).
The behavior is that when you create a mesh, the nslicer is deleted and vice versa.

I mostly tested this manually. I added a print in the temp mesh's update, and made sure that when any axis gets deleted or updated, the print would trigger.

I could add an auto test?! I need to look into that, but wanted to send this out to get some feedback on the approach.

Next up: I'll add the algorithm for actually updating the render buffers in the temp mesh.

doc: https://www.notion.so/rive-app/9-Slice-Tech-Proposal-Image-only-50b25ea8e79c4efabb681110e288f064#15f3a49ce3534baeafc31c37fb30cc0b

Diffs=
f99c93181 editor: setting up the update callbacks for n-slicing (#7869)

Co-authored-by: Susan Wang <[email protected]>

.rive_head

@@ -1 +1 @@
-85343a4e1c287922f872d14172167af72b4c3358
+f99c93181b2073db07b0c54f766648ce56c89df9

dev/defs/layout/n_slicer.json

@@ -4,5 +4,5 @@
     "int": 493,
     "string": "nslicer"
   },
-  "extends": "component.json"
+  "extends": "container_component.json"
 }

include/rive/generated/layout/n_slicer_base.hpp

@@ -1,12 +1,12 @@
 #ifndef _RIVE_N_SLICER_BASE_HPP_
 #define _RIVE_N_SLICER_BASE_HPP_
-#include "rive/component.hpp"
+#include "rive/container_component.hpp"
 namespace rive
 {
-class NSlicerBase : public Component
+class NSlicerBase : public ContainerComponent
 {
 protected:
-    typedef Component Super;
+    typedef ContainerComponent Super;
 
 public:
     static const uint16_t typeKey = 493;
@@ -18,6 +18,7 @@ class NSlicerBase : public Component
         switch (typeKey)
         {
             case NSlicerBase::typeKey:
+            case ContainerComponentBase::typeKey:
             case ComponentBase::typeKey:
                 return true;
             default: