[RozmiDan]

Rework batch execution to fix resource cleanup, transaction ownership, and error handling. Add a simple batch API for native fbx and database/sql.

• Keep one prepared statement and use its metadata throughout the batch lifetime.
• Reuse PreparedBatch between executions and clear queued data without closing the server batch.
• Fix protocol response handling, context cancellation, and retry safety.
• Add Exec(sql, BatchRows) to send and execute a complete set of parameters in one call.
• Fix BatchInsert cleanup and source error handling.
• Validate batch options and return -1 when affected row counts are unknown.
• Add PreparedBatch.Info to read server batch buffer information.
• Read batch completion entries incrementally instead of allocating arrays from header counts.