feat: add json output test for vet command

Author: atsai1220

test/e2e/test_suites/test_kcl_vet_output_json_1/input

@@ -0,0 +1 @@
+kcl vet --format json --schema User data.json main.k --output json

test/e2e/test_suites/test_kcl_vet_output_json_1/stderr

@@ -0,0 +1,21 @@
+[
+  {
+    "errorType": "EvaluationError",
+    "file": "data.json",
+    "line": 1,
+    "column": 1,
+    "details": {
+      "errorMessage": "Instance check failed",
+      "codeSnippet": "{"
+    },
+    "schema": {
+      "filepath": "main.k",
+      "lineInFile": 10,
+      "columnInFile": 1,
+      "details": {
+        "errorMessage": "Check failed on the condition",
+        "codeSnippet": "age > 10"
+      }
+    }
+  }
+]

test/e2e/test_suites/test_kcl_vet_output_json_1/stdout

@@ -0,0 +1,17 @@
+{
+  "name": "Alice",
+  "age": 5,
+  "message": "This is Alice",
+  "data": {
+    "id": 1,
+    "value": "value1"
+  },
+  "labels": {
+    "key": "value"
+  },
+  "hc": [
+    1,
+    2,
+    3
+  ]
+}

test/e2e/test_suites/test_kcl_vet_output_json_1/test_space/data.json

@@ -0,0 +1,15 @@
+schema User:
+    name: str
+    age: int
+    message?: str
+    data: Data
+    labels: {str:}
+    hc: [int]
+
+    check:
+        age > 10
+
+schema Data:
+    id: int
+    value: str
+