[SPARK-14942][SQL][STREAMING] Reduce delay between batch construction and execution
## Problem
Currently in `StreamExecution`, [we first run the batch, then construct the next](https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/StreamExecution.scala#L165):
```scala
if (dataAvailable) runBatch()
constructNextBatch()
```
This is good when we run batches ASAP, where data would get processed in the **very next batch**:
However, when we run batches at trigger like `ProcessTime("1 minute")`, data - such as _y_ below - may not get processed in the very next batch i.e. _batch 1_, but in _batch 2_:
## What changes were proposed in this pull request?
This patch reverses the order of `constructNextBatch()` and `runBatch()`. After this patch, data would get processed in the **very next batch**, i.e. _batch 1_:
In addition, this patch alters when we do `currentBatchId += 1`: let's do that when the processing of the current batch's data is completed, so we won't bother passing `currentBatchId + 1` or `currentBatchId - 1` to states or sinks.
## How was this patch tested?
New added test case. Also this should be covered by existing test suits, e.g. stress tests and others.
Author: Liwei Lin <lwlin7@gmail.com>
Closes #12725 from lw-lin/construct-before-run-3.
95f4fbae52
