Refactor to use new duckdb-go-api helper functions

[JC1738]

Summary

• Add helper functions to duckdb-go-api for error handling and vector assignment
• Refactor DuckArrow to use these helpers, reducing boilerplate and memory leak risk

New Helper Functions (in duckdb-go-api)

Error Handling:

• SetBindError(info BindInfo, format string, args...) - for table function bind callbacks
• SetInitError(info InitInfo, format string, args...) - for table function init callbacks
• SetFunctionError(info FunctionInfo, format string, args...) - for table function scan callbacks

Vector Assignment:

• AssignStringToVector(vec Vector, idx int, str string) - for VARCHAR columns
• AssignBytesToVector(vec Vector, idx int, data []byte) - for BLOB columns

Changes

File	Changes
table_function.go	Replace ~8 error handling blocks, update string/binary conversions
config_function.go	Use AssignStringToVector for result message
version_function.go	Use AssignStringToVector for version output
duckdb-go-api	Update submodule with new helper functions
tests/*.sql	Fix credentials and TLS settings

Impact

Metric	Before	After
Error handling lines	~60 lines	~15 lines
String assignment boilerplate	Inconsistent	Centralized
Memory leak risk	Higher (manual CString/free)	Lower (encapsulated)

Test plan

• Unit tests pass (make test-unit)
• Integration tests pass (make test-all)
• Build succeeds (make build)
• Code review completed