Support table-model OBJECT writes and OBJECT result decoding

[CritasWang]

Summary

Add table-model OBJECT write support and the read-side display semantics to the Rust
client, mirroring the already-merged SDK implementations:

• Go: Support OBJECT data type in tablet write iotdb-client-go#175
• Node.js: Support OBJECT data type in table-model tablet writes iotdb-client-nodejs#25
• C#: Support OBJECT data type in table-model tablet writes iotdb-client-csharp#64

No Thrift IDL / generated src/protocol/ changes.

What changed

• TSDataType::Object = 12 (official TSFile code) + from_code.
• Value::Object(Vec<u8>) carrying the already-framed OBJECT segment
  [1 byte isEOF][8 byte big-endian offset][content], plus
  object_bytes_to_string producing (Object) 1023 B / (Object) 1.00 KB /
  (Object) 1.00 MB / (Object) 1.00 GB (same thresholds as Go/Node/C#).
• Tablet::build_object_value(is_eof, offset, content) and
  Tablet::set_object_value_at(...) (Go SetObjectValueAt counterpart) with
  column-type / row / column / negative-offset validation. Overwriting a null cell sets
  the Option back to Some, which clears the null bit Rust derives at serialization
  time (Go's unmarkNullValueAt).
• serialize_values/record serialization write OBJECT columns with the same
  4-byte BE length-prefixed binary layout as BLOB; insertTablet now sends type code 12.
• TsBlock BinaryArray decoding accepts OBJECT and keeps the raw 8-byte BE size +
  internal path; SessionDataSet::apply_logical_type formats select file OBJECT
  metadata into Value::String("(Object) 1.00 KB") while select READ_OBJECT(file)
  still returns raw Value::Blob.
• Documentation in README/README_ZH and an OBJECT demo in examples/table_session.rs
  (probes server support and skips on IoTDB < 2.0.8, keeping CI green on 2.0.6).

Tests

Golden-byte / mock tests (no server):

• data_type_codes_match_spec / data_type_from_code_round_trips include 12.
• value::object_bytes_to_string_* unit boundaries and short-input error.
• tablet::build_object_value_frames_segments,
  set_object_value_at_writes_whole_and_segmented_rows,
  set_object_value_at_clears_previously_null_cell,
  set_object_value_at_rejects_invalid_inputs; all_types_known_bytes /
  all_types_null_placeholders now cover OBJECT with byte-exact expectations.
• tsblock::binary_array_object_metadata_and_nulls and truncated-payload error.
• dataset::object_column_renders_size_summary /
  short_object_metadata_is_decode_error; READ_OBJECT stays BLOB via the existing
  logical-type retagging tests.
• session::insert_tablet_request_carries_object_type_12 builds the actual
  TSInsertTabletReq and checks types == [11, 12], values buffer, categories and
  writeToTable.
• table_session::live_object_write_roundtrip: whole object, 512+512 segmented
  inserts, null row, count(*), READ_OBJECT byte round-trip and select file
  summary; probes OBJECT support and skips exactly like Go PR 175's e2e.

Local verification: cargo fmt, cargo clippy --all-targets -- -D warnings
(default and --features tls), ./tools/check-license.sh,
cargo test (126 passed) and cargo test --features tls (137 passed);
cargo build --example table_session compiles.