[MINOR][CORE] Validate spark.deploy.defaultCores value during config …

…setting

### What changes were proposed in this pull request?

This aims to move `spark.deploy.defaultCores` validation logic to config setting.

### Why are the changes needed?

In order to ensure the value range by early checking.

### Does this PR introduce _any_ user-facing change?

No. `Spark Master` will fail to start in both cases, *before* and *after*.

### How was this patch tested?

Manual review.

### Was this patch authored or co-authored using generative AI tooling?

No.

Closes #43655 from dongjoon-hyun/spark.deploy.defaultCores.

Authored-by: Dongjoon Hyun <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>

core/src/main/scala/org/apache/spark/deploy/master/Master.scala

@@ -24,7 +24,7 @@ import java.util.concurrent.{ScheduledFuture, TimeUnit}
 import scala.collection.mutable.{ArrayBuffer, HashMap, HashSet}
 import scala.util.Random
 
-import org.apache.spark.{SecurityManager, SparkConf, SparkException}
+import org.apache.spark.{SecurityManager, SparkConf}
 import org.apache.spark.deploy.{ApplicationDescription, DriverDescription, ExecutorState}
 import org.apache.spark.deploy.DeployMessages._
 import org.apache.spark.deploy.master.DriverState.DriverState
@@ -119,9 +119,6 @@ private[deploy] class Master(
   // Default maxCores for applications that don't specify it (i.e. pass Int.MaxValue)
   private val defaultCores = conf.get(DEFAULT_CORES)
   val reverseProxy = conf.get(UI_REVERSE_PROXY)
-  if (defaultCores < 1) {
-    throw new SparkException(s"${DEFAULT_CORES.key} must be positive")
-  }
   val historyServerUrl = conf.get(MASTER_UI_HISTORY_SERVER_URL)
 
   // Alternative application submission gateway that is stable across Spark versions

core/src/main/scala/org/apache/spark/internal/config/Deploy.scala

@@ -73,6 +73,7 @@ private[spark] object Deploy {
   val DEFAULT_CORES = ConfigBuilder("spark.deploy.defaultCores")
     .version("0.9.0")
     .intConf
+    .checkValue(_ > 0, "spark.deploy.defaultCores must be positive.")
     .createWithDefault(Int.MaxValue)
 
   val MAX_DRIVERS = ConfigBuilder("spark.deploy.maxDrivers")