Provide option to clean up DFS sources after each commit

Since DeltaStreamer makes heavily use of file listing, if the source contains a lot of tiny files, this could  quickly become a bottle neck. We need a way to delete/archive files once processed by DeltaStreamer. 

It seems like the best way to reliably clean up the source is after DeltaSync commit the checkpoint successfully. We could add a new public method to Source e.g. `postCommit()` and invoke it after each successful commit 

Reference:

[https://spark.apache.org/docs/latest/structured-streaming-programming-guide.html#input-sources]

 

## JIRA info

- Link: https://issues.apache.org/jira/browse/HUDI-1348
- Type: Improvement

---

## Comments

21/Oct/20 12:59;vho;[~vinoth] what do you think about this? I'm not sure if there's already a solution ;;;

---

24/Oct/20 02:12;vinoth;[~vho] thanks For bringing this up. It seems valuable to support such an option. 
I am not aware of any other work along these lines. [~bhasudha] is looking into parallelism for input source listing;;;

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08/Aug/21 20:17;githubbot;hudi-bot edited a comment on pull request #2210:
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09/Aug/21 04:21;githubbot;hudi-bot edited a comment on pull request #2210:
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11/Aug/21 22:25;githubbot;hudi-bot edited a comment on pull request #2210:
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## CI report:

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11/Aug/21 22:28;githubbot;hudi-bot edited a comment on pull request #2210:
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11/Aug/21 23:27;githubbot;hudi-bot edited a comment on pull request #2210:
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