Improve DuckDB::TableFunction C API coverage

[suketa]

Overview

DuckDB::TableFunction and its related classes (BindInfo, InitInfo, FunctionInfo) are missing several features from the DuckDB C API. This issue tracks the full list.

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Currently implemented

Class	Methods
TableFunction	name=, add_parameter, add_named_parameter, bind, init, execute
BindInfo	parameter_count, get_parameter, get_named_parameter, add_result_column, set_cardinality, set_error
InitInfo	set_error
FunctionInfo	set_error

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Missing from DuckDB::TableFunction

• local_init(&block) — wrap duckdb_table_function_set_local_init. Enables per-thread local initialization for parallel execution.
• supports_projection_pushdown(bool) — wrap duckdb_table_function_supports_projection_pushdown. Tells DuckDB the function can skip columns not needed by the query.

Missing from DuckDB::BindInfo

• get_extra_info — wrap duckdb_bind_get_extra_info. Retrieve extra info set on the function via set_extra_info.
• set_bind_data(data, destroy) — wrap duckdb_bind_set_bind_data. Store user data during bind phase for use in init/execute callbacks.
• get_client_context — wrap duckdb_table_function_get_client_context. Provides access to the client connection context during bind.

Missing from DuckDB::InitInfo

• get_extra_info — wrap duckdb_init_get_extra_info. Retrieve extra info set on the function.
• get_bind_data — wrap duckdb_init_get_bind_data. Access data stored during the bind phase.
• set_init_data(data, destroy) — wrap duckdb_init_set_init_data. Store init state for use in the execute callback.
• column_count — wrap duckdb_init_get_column_count. Number of columns DuckDB actually needs (for projection pushdown).
• column_index(i) — wrap duckdb_init_get_column_index. Which column index DuckDB needs (for projection pushdown).
• set_max_threads(n) — wrap duckdb_init_set_max_threads. Controls parallelism for table function execution.

Missing from DuckDB::FunctionInfo

• get_bind_data — wrap duckdb_function_get_bind_data. Access bind-phase user data in the execute callback.
• get_init_data — wrap duckdb_function_get_init_data. Access init-phase data in the execute callback.
• get_local_init_data — wrap duckdb_function_get_local_init_data. Access per-thread local init data in the execute callback (parallel execution).

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Priority notes

• BindInfo#set_bind_data + FunctionInfo#get_bind_data — highest value; enables stateful functions that compute schema dynamically at bind time and pass state to execute
• Projection pushdown (supports_projection_pushdown + InitInfo#column_count / column_index) — significant performance feature for large tables; allows skipping unneeded columns entirely
• local_init + get_local_init_data — needed for correct parallel execution support