## What changes were proposed in this pull request?

Currently, `readBatches` accumulator of `InMemoryTableScanExec` is updated only when `spark.sql.inMemoryColumnarStorage.partitionPruning` is true. Although this metric is used for only testing purpose, we had better have correct metric without considering SQL options.

## How was this patch tested?

Pass the Jenkins tests (including a new testcase).

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #13870 from dongjoon-hyun/SPARK-16165.