v4.3.0rc1

• Add optional Rust kernel backend for use_kernel=True, installable via the new databricks-sql-connector[kernel] extra (requires Python >= 3.10). Routes connections through the native databricks-sql-kernel client, with parity work across cursor-state tracking, metadata, logging (kernel logs surface through Python logging), staging fail-loud behavior, error context, and sync cancel (#824, #825, #830, #838, #839 by @vikrantpuppala)
• Revert the thrift 0.23.0 bump that broke installation on DBR LTS (ES-1960554) (#840 by @vikrantpuppala)