Show NestedInputs in the Inputs panel of the parent artboard

One feature missing from the nested inputs implementation was the ability to see the nested input values in the parent artboard's input panel. This update adds this feature, grouping the nested input by its nested artboard.

https://github.com/rive-app/rive/assets/186340/6892826f-14e0-46e7-a9bf-e629e005e85c

Diffs=
3b32d2431 Show NestedInputs in the Inputs panel of the parent artboard (#6107)

Co-authored-by: Philip Chung <[email protected]>

.rive_head

@@ -1 +1 @@
-7227975fb1afd53cbb9d5c6c3149db17606a606f
+3b32d24314be7d877a11b8069622d6d6115383b7

dev/defs/animation/state_machine_component_nested_artboard.json

@@ -0,0 +1,23 @@
+{
+  "name": "StateMachineComponentNestedArtboard",
+  "key": {
+    "int": 172,
+    "string": "statemachinecomponentnestedartboard"
+  },
+  "extends": "animation/state_machine_component_folder.json",
+  "runtime": false,
+  "properties": {
+    "nestedArtboardId": {
+      "type": "Id",
+      "typeRuntime": "uint",
+      "initialValue": "Core.missingId",
+      "initialValueRuntime": "-1",
+      "key": {
+        "int": 404,
+        "string": "nestedartboardid"
+      },
+      "description": "Id of the Artboard represented by this component.",
+      "runtime": false
+    }
+  }
+}

dev/defs/animation/state_machine_nested_input.json

@@ -0,0 +1,23 @@
+{
+  "name": "StateMachineNestedInput",
+  "key": {
+    "int": 173,
+    "string": "statemachinenestedinput"
+  },
+  "extends": "animation/state_machine_component.json",
+  "runtime": false,
+  "properties": {
+    "nestedInputId": {
+      "type": "Id",
+      "typeRuntime": "uint",
+      "initialValue": "Core.missingId",
+      "initialValueRuntime": "-1",
+      "key": {
+        "int": 403,
+        "string": "nestedinputid"
+      },
+      "description": "Id of the NestedInput.",
+      "runtime": false
+    }
+  }
+}