[SPARK-52299][CORE] replace deprecated JsonNode.fields

### What changes were proposed in this pull request?
JsonNode.fields is deprecated, and is supposed to be replaced as JsonNode.properties.

### Why are the changes needed?
Without the fix, there're warning during compile:

[warn] /path/to/spark/core/src/main/scala/org/apache/spark/util/JsonProtocol.scala:1026:10: method fields in class JsonNode is deprecated
[warn] Applicable -Wconf / nowarn filters for this warning: msg=<part of the message>, cat=deprecation, site=org.apache.spark.util.JsonProtocol.taskResourceRequestMapFromJson, origin=com.fasterxml.jackson.databind.JsonNode.fields
[warn]     json.fields().asScala.collect { case field =>
[warn]          ^

### Does this PR introduce _any_ user-facing change?
No, it only fixes compilation warning.

### How was this patch tested?
after the fix, no such warning during compilation. all ut passes.

### Was this patch authored or co-authored using generative AI tooling?
No

Closes apache#51011 from yuexing/SPARK-52299.

Authored-by: xingyue <xingyue@baidu.com>
Signed-off-by: yangjie01 <yangjie01@baidu.com>

Author: yuexing

core/src/main/scala/org/apache/spark/util/JsonProtocol.scala

@@ -1023,14 +1023,14 @@ private[spark] class JsonProtocol(sparkConf: SparkConf) extends JsonUtils {
   }
 
   def taskResourceRequestMapFromJson(json: JsonNode): Map[String, TaskResourceRequest] = {
-    json.fields().asScala.collect { case field =>
+    json.properties().asScala.collect { case field =>
       val req = taskResourceRequestFromJson(field.getValue)
       (field.getKey, req)
     }.toMap
   }
 
   def executorResourceRequestMapFromJson(json: JsonNode): Map[String, ExecutorResourceRequest] = {
-    json.fields().asScala.collect { case field =>
+    json.properties().asScala.collect { case field =>
       val req = executorResourceRequestFromJson(field.getValue)
       (field.getKey, req)
     }.toMap
@@ -1543,7 +1543,7 @@ private[spark] class JsonProtocol(sparkConf: SparkConf) extends JsonUtils {
 
   def resourcesMapFromJson(json: JsonNode): Map[String, ResourceInformation] = {
     assert(json.isObject, s"expected object, got ${json.getNodeType}")
-    json.fields.asScala.map { field =>
+    json.properties.asScala.map { field =>
       val resourceInfo = ResourceInformation.parseJson(field.getValue.toString)
       (field.getKey, resourceInfo)
     }.toMap
@@ -1555,7 +1555,7 @@ private[spark] class JsonProtocol(sparkConf: SparkConf) extends JsonUtils {
 
   def mapFromJson(json: JsonNode): Map[String, String] = {
     assert(json.isObject, s"expected object, got ${json.getNodeType}")
-    json.fields.asScala.map { field =>
+    json.properties.asScala.map { field =>
       (field.getKey, field.getValue.extractString)
     }.toMap
   }

core/src/test/scala/org/apache/spark/util/JsonProtocolSuite.scala

@@ -1356,7 +1356,7 @@ private[spark] object jsonProtocolSuite extends Assertions {
       case ((key1, values1: scala.collection.Seq[(String, String)]),
         (key2, values2: scala.collection.Seq[(String, String)])) =>
         assert(key1 === key2)
-        values1.zip(values2).foreach { case (v1, v2) => assert(v1 === v2) }
+        assert(values1.toMap == values2.toMap)
     }
   }