[SPARK-22124][SQL] Sample and Limit should also defer input evaluation under codegen

## What changes were proposed in this pull request?

We can override `usedInputs` to claim that an operator defers input evaluation. `Sample` and `Limit` are two operators which should claim it but don't. We should do it.

## How was this patch tested?

Existing tests.

Author: Liang-Chi Hsieh <viirya@gmail.com>

Closes #19345 from viirya/SPARK-22124.