spark git commit: [SPARK-19644][SQL] Clean up Scala reflection garbage after creating Encoder (branch-2.2)

Repository: spark Updated Branches: refs/heads/branch-2.2 6b4ec22e3 -> 8b7f72ed3 [SPARK-19644][SQL] Clean up Scala reflection garbage after creating Encoder (branch-2.2) ## What changes were proposed in this pull request? Backport #19687 to branch-2.2. The major difference is

spark git commit: [SPARK-19644][SQL] Clean up Scala reflection garbage after creating Encoder

Repository: spark Updated Branches: refs/heads/master 5ebdcd185 -> 24ea781cd [SPARK-19644][SQL] Clean up Scala reflection garbage after creating Encoder ## What changes were proposed in this pull request? Because of the memory leak issue in `scala.reflect.api.Types.TypeApi.<:<`