.github/pull_request_template.md

## Description


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<hr>

This PR has:
- [ ] been self-reviewed.
    - [ ] concurrent read
    - [ ] concurrent write
    - [ ] concurrent read and write 
- [ ] added documentation for new or modified features or behaviors.
- [ ] added Javadocs for most classes and all non-trivial methods. 
- [ ] added or updated version, __license__, or notice information
- [ ] added comments explaining the "why" and the intent of the code wherever would not be obvious 
  for an unfamiliar reader.
- [ ] added unit tests or modified existing tests to cover new code paths, ensuring the threshold 
  for code coverage.
- [ ] added integration tests.
- [ ] been tested in a test IoTDB cluster.

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<hr>

##### Key changed/added classes (or packages if there are too many classes) in this PR