[MINOR][SQL] Standardize 'continuous queries' to 'streaming Datasets/DataFrames'

## What changes were proposed in this pull request?

This patch does some replacing (as `streaming Datasets/DataFrames` is the term we've chosen in [SPARK-15593](https://github.com/apache/spark/commit/00c310133df4f3893dd90d801168c2ab9841b102)):
 - `continuous queries` -> `streaming Datasets/DataFrames`
 - `non-continuous queries` -> `non-streaming Datasets/DataFrames`

This patch also adds `test("check foreach() can only be called on streaming Datasets/DataFrames")`.

## How was this patch tested?

N/A

Author: Liwei Lin <lwlin7@gmail.com>

Closes #13595 from lw-lin/continuous-queries-to-streaming-dss-dfs.