Crash if inherited property is structurally equal but not reference identical

If a definition defines a property, and inherits from another definition that also defines the property:

• If the properties are reference identical, it's allowed
• If the properties are equivalent (but not reference identical), the tool crashes

Organic PRs hitting problem

• https://github.com/Azure/azure-rest-api-specs/actions/runs/25541171453

Test Cases

• https://github.com/Azure/openapi-diff/pull/481

Pass - Reference Identical

{
  "swagger": "2.0",
  "info": {
    "title": "structural-equality",
    "version": "1.0"
  },
  "paths": {},
  "definitions": {
    "Foo": {
      "type": "object",
      "properties": {
        "bar": {
          "$ref": "#/definitions/MyObject"
        }
      },
      "allOf": [
        {
          "$ref": "#/definitions/Foo2"
        }
      ]
    },
    "Foo2": {
      "type": "object",
      "properties": {
        "bar": {
          "$ref": "#/definitions/MyObject"
        }
      }
    },
    "MyObject": {
      "type": "object",
      "additionalProperties": {
        "type": "string"
      }
    }
  }
}

Fail - Structurally Equal

{
  "swagger": "2.0",
  "info": {
    "title": "structural-equality",
    "version": "1.0"
  },
  "paths": {},
  "definitions": {
    "Foo": {
      "type": "object",
      "properties": {
        "bar": {
          "type": "object",
          "additionalProperties": {
            "type": "string"
          }
        }
      },
      "allOf": [
        {
          "$ref": "#/definitions/Foo2"
        }
      ]
    },
    "Foo2": {
      "type": "object",
      "properties": {
        "bar": {
          "type": "object",
          "additionalProperties": {
            "type": "string"
          }
        }
      }
    }
  }
}

Error

    incompatible properties : bar
      definitions/Foo/properties/bar
        at file:///home/mharder/openapi-diff-mh/incompat-prop/src/test/specs/incompatible-properties/structural-equality-fail.json#L12:8
      definitions/Foo2/properties/bar
        at file:///home/mharder/openapi-diff-mh/incompat-prop/src/test/specs/incompatible-properties/structural-equality-fail.json#L28:8