[SPARK-27083][SQL][FOLLOW-UP] Rename spark.sql.subquery.reuse to spark.sql.execution.subquery.reuse.enabled

### What changes were proposed in this pull request?
This PR is to rename spark.sql.subquery.reuse to spark.sql.execution.subquery.reuse.enabled

### Why are the changes needed?
Make it consistent and clear.

### Does this PR introduce any user-facing change?
N/A. This is a [new conf added in Spark 3.0](apache#23998)

### How was this patch tested?
N/A

Closes apache#27346 from gatorsmile/spark27083.

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

Author: gatorsmile

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

@@ -1053,7 +1053,7 @@ object SQLConf {
     .booleanConf
     .createWithDefault(true)
 
-  val SUBQUERY_REUSE_ENABLED = buildConf("spark.sql.subquery.reuse")
+  val SUBQUERY_REUSE_ENABLED = buildConf("spark.sql.execution.subquery.reuse.enabled")
     .internal()
     .doc("When true, the planner will try to find out duplicated subqueries and re-use them.")
     .booleanConf