### What changes were proposed in this pull request?
When using dynamic partition overwrite, each task has its working dir under staging dir like `stagingDir/.spark-staging-{jobId}`, each task commits to `outputPath/.spark-staging-{jobId}/{partitionId}/part-{taskId}-{jobId}{ext}`.
When speculation enable, multiple task attempts would be setup for one task, **they have same task id and they would commit to same file concurrently**. Due to host done or node preemption, the partly-committed files aren't cleaned up, a FileAlreadyExistsException would be raised in this situation, resulting in job failure.
I don't try to change task commit process for dynamic partition overwrite, like adding attempt id to task working dir for each attempts and committing to final output dir via a new outputCommitCoordinator, here is reason:
1. `FileOutputCommitter` already has commit coordinator for each task attempts, we can leverage it rather than build a new one.
2. To say the least, we implement a coordinator solving task attempts commit conflict, suppose a severe case, application master failover, tasks with same attempt id and same task id would commit to same files, the `FileAlreadyExistsException` risk still exists
In this pr, I leverage FileOutputCommitter to solve the problem:
1. when initing a write job description, set `outputPath/.spark-staging-{jobId}` as the output dir
2. each task attempt writes output to `outputPath/.spark-staging-{jobId}/_temporary/${appAttemptId}/_temporary/${taskAttemptId}/{partitionId}/part-{taskId}-{jobId}{ext}`
3. leverage `FileOutputCommitter` coordinator, write job firstly commits output to `outputPath/.spark-staging-{jobId}/{partitionId}`
4. for dynamic partition overwrite, write job finally move `outputPath/.spark-staging-{jobId}/{partitionId}` to `outputPath/{partitionId}`
### Why are the changes needed?
Without this pr, dynamic partition overwrite would fail
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
added UT.
Closes#29000 from WinkerDu/master-fix-dynamic-partition-multi-commit.
Authored-by: duripeng <duripeng@baidu.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
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