[CLIENT-PY]Optimize the performance of filling null values

[fuwei3140]

Description

Optimize the performance of filling null values by bitmap. When the amount of data reaches millions and contains a small number of null values, reduce time by about 90%.
Related to #4242

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

[HTHou]

LGTM