[SPARK-31234][SQL][FOLLOW-UP] ResetCommand should not affect static SQL Configuration

### What changes were proposed in this pull request?
This PR is the follow-up PR of #28003

- add a migration guide
- add an end-to-end test case.

### Why are the changes needed?
The original PR made the major behavior change in the user-facing RESET command.

### Does this PR introduce any user-facing change?
No

### How was this patch tested?
Added a new end-to-end test

Closes #28265 from gatorsmile/spark-31234followup.

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

Author: gatorsmile

docs/core-migration-guide.md

@@ -25,7 +25,7 @@ license: |
 ## Upgrading from Core 2.4 to 3.0
 
 - The `org.apache.spark.ExecutorPlugin` interface and related configuration has been replaced with
-  `org.apache.spark.plugin.SparkPlugin`, which adds new functionality. Plugins using the old
+  `org.apache.spark.api.plugin.SparkPlugin`, which adds new functionality. Plugins using the old
   interface must be modified to extend the new interfaces. Check the
   [Monitoring](monitoring.html) guide for more details.
 

docs/sql-migration-guide.md

@@ -216,6 +216,10 @@ license: |
 
     * The decimal string representation can be different between Hive 1.2 and Hive 2.3 when using `TRANSFORM` operator in SQL for script transformation, which depends on hive's behavior. In Hive 1.2, the string representation omits trailing zeroes. But in Hive 2.3, it is always padded to 18 digits with trailing zeroes if necessary.
 
+## Upgrading from Spark SQL 2.4.5 to 2.4.6
+
+  - In Spark 2.4.6, the `RESET` command does not reset the static SQL configuration values to the default. It only clears the runtime SQL configuration values.
+
 ## Upgrading from Spark SQL 2.4.4 to 2.4.5
 
   - Since Spark 2.4.5, `TRUNCATE TABLE` command tries to set back original permission and ACLs during re-creating the table/partition paths. To restore the behaviour of earlier versions, set `spark.sql.truncateTable.ignorePermissionAcl.enabled` to `true`.

sql/catalyst/src/main/scala/org/apache/spark/sql/internal/StaticSQLConf.scala

@@ -47,6 +47,9 @@ object StaticSQLConf {
     .internal()
     .version("2.1.0")
     .stringConf
+    // System preserved database should not exists in metastore. However it's hard to guarantee it
+    // for every session, because case-sensitivity differs. Here we always lowercase it to make our
+    // life easier.
     .transform(_.toLowerCase(Locale.ROOT))
     .createWithDefault("global_temp")
 

sql/core/src/main/scala/org/apache/spark/sql/internal/SharedState.scala

@@ -153,9 +153,6 @@ private[sql] class SharedState(
    * A manager for global temporary views.
    */
   lazy val globalTempViewManager: GlobalTempViewManager = {
-    // System preserved database should not exists in metastore. However it's hard to guarantee it
-    // for every session, because case-sensitivity differs. Here we always lowercase it to make our
-    // life easier.
     val globalTempDB = conf.get(GLOBAL_TEMP_DATABASE)
     if (externalCatalog.databaseExists(globalTempDB)) {
       throw new SparkException(

sql/core/src/test/scala/org/apache/spark/sql/SparkSessionBuilderSuite.scala

@@ -22,6 +22,7 @@ import org.scalatest.BeforeAndAfterEach
 import org.apache.spark.{SparkConf, SparkContext, SparkFunSuite}
 import org.apache.spark.internal.config.UI.UI_ENABLED
 import org.apache.spark.sql.internal.SQLConf
+import org.apache.spark.sql.internal.StaticSQLConf.GLOBAL_TEMP_DATABASE
 
 /**
  * Test cases for the builder pattern of [[SparkSession]].
@@ -152,4 +153,19 @@ class SparkSessionBuilderSuite extends SparkFunSuite with BeforeAndAfterEach {
       session.sparkContext.hadoopConfiguration.unset(mySpecialKey)
     }
   }
+
+  test("SPARK-31234: RESET command will not change static sql configs and " +
+    "spark context conf values in SessionState") {
+    val session = SparkSession.builder()
+      .master("local")
+      .config(GLOBAL_TEMP_DATABASE.key, value = "globalTempDB-SPARK-31234")
+      .config("spark.app.name", "test-app-SPARK-31234")
+      .getOrCreate()
+
+    assert(session.sessionState.conf.getConfString("spark.app.name") === "test-app-SPARK-31234")
+    assert(session.sessionState.conf.getConf(GLOBAL_TEMP_DATABASE) === "globaltempdb-spark-31234")
+    session.sql("RESET")
+    assert(session.sessionState.conf.getConfString("spark.app.name") === "test-app-SPARK-31234")
+    assert(session.sessionState.conf.getConf(GLOBAL_TEMP_DATABASE) === "globaltempdb-spark-31234")
+  }
 }

sql/core/src/test/scala/org/apache/spark/sql/internal/SQLConfSuite.scala

@@ -116,7 +116,7 @@ class SQLConfSuite extends QueryTest with SharedSparkSession {
     }
   }
 
-  test("reset will not change static sql configs and spark core configs") {
+  test("SPARK-31234: reset will not change static sql configs and spark core configs") {
     val conf = spark.sparkContext.getConf.getAll.toMap
     val appName = conf.get("spark.app.name")
     val driverHost = conf.get("spark.driver.host")