[SPARK-14579][SQL] Fix a race condition in StreamExecution.processAllAvailable

## What changes were proposed in this pull request?

There is a race condition in `StreamExecution.processAllAvailable`. Here is an execution order to reproduce it.

| Time        |Thread 1           | MicroBatchThread  |
|:-------------:|:-------------:|:-----:|
| 1 | |  `dataAvailable in constructNextBatch` returns false  |
| 2 | addData(newData)      |   |
| 3 | `noNewData = false` in  processAllAvailable |  |
| 4 | | noNewData = true |
| 5 | `noNewData` is true so just return | |

The root cause is that `checking dataAvailable and change noNewData to true` is not atomic. This PR puts these two actions into `synchronized` to make sure they are atomic.

In addition, this PR also has the following changes:

- Make `committedOffsets` and `availableOffsets` volatile to make sure they can be seen in other threads.
- Copy the reference of `availableOffsets` to a local variable so that `sourceStatuses` can use a snapshot of `availableOffsets`.

## How was this patch tested?

Existing unit tests.

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #12339 from zsxwing/race-condition.