session python object

[hongzhi-gao]

Description

This PR adds OBJECT type support to the Python session client for both write and read paths, and adds test coverage for object-type serialization and round-trip query behavior.

Content1: Add OBJECT type definition and write-path support

• Added TSDataType.OBJECT = 12 in Python constants to align with server-side enum semantics.
• Extended write serialization in:
  • Session.value_to_bytes() (iotdb-client/client-py/iotdb/Session.py)
  • Tablet.get_binary_values() (iotdb-client/client-py/iotdb/utils/Tablet.py)
  • NumpyTablet.get_binary_values() (iotdb-client/client-py/iotdb/utils/NumpyTablet.py)
• Design choice: treat OBJECT as binary payload (length-prefixed bytes), consistent with existing TEXT/STRING/BLOB binary transport pattern and Java-side session behavior.

Content2: Add OBJECT type read-path support

• Extended TsBlock decoding to accept and parse OBJECT columns:
  • read_column_types() and read_binary_column() in iotdb-client/client-py/iotdb/tsfile/utils/tsblock_serde.py
• Extended dataset conversion and field access:
  • iotdb-client/client-py/iotdb/utils/iotdb_rpc_dataset.py
  • iotdb-client/client-py/iotdb/utils/Field.py
  • iotdb-client/client-py/iotdb/utils/SessionDataSet.py
• Design choice: return OBJECT as raw bytes in Python APIs (same practical behavior as BLOB-style handling) for deterministic round-trip verification.

Content3: Tests for OBJECT type

• Added integration test:
  • iotdb-client/client-py/tests/integration/test_object_type.py
  • Covers write and read round-trip for OBJECT values using Tablet, NumpyTablet, and record APIs.
• Extended unit test:
  • iotdb-client/client-py/tests/unit/test_numpy_tablet.py
  • Verifies OBJECT serialization parity between Tablet and NumpyTablet.

---

This PR has:

• been self-reviewed.
• added documentation for new or modified features or behaviors.
• 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.

---

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

• iotdb-client/client-py/iotdb/utils/IoTDBConstants.py
• iotdb-client/client-py/iotdb/Session.py
• iotdb-client/client-py/iotdb/utils/Tablet.py
• iotdb-client/client-py/iotdb/utils/NumpyTablet.py
• iotdb-client/client-py/iotdb/tsfile/utils/tsblock_serde.py
• iotdb-client/client-py/iotdb/utils/iotdb_rpc_dataset.py
• iotdb-client/client-py/iotdb/utils/Field.py
• iotdb-client/client-py/iotdb/utils/SessionDataSet.py
• iotdb-client/client-py/tests/integration/test_object_type.py
• iotdb-client/client-py/tests/unit/test_numpy_tablet.py