[SPARK-22542][SQL] remove unused features in ColumnarBatch

## What changes were proposed in this pull request?

`ColumnarBatch` provides features to do fast filter and project in a columnar fashion, however this feature is never used by Spark, as Spark uses whole stage codegen and processes the data in a row fashion. This PR proposes to remove these unused features as we won't switch to columnar execution in the near future. Even we do, I think this part needs a proper redesign.

This is also a step to make `ColumnVector` public, as we don't wanna expose these features to users.

## How was this patch tested?

existing tests

Author: Wenchen Fan <wenchen@databricks.com>

Closes #19766 from cloud-fan/vector.