feat: extend sql execute API

Adds a new exported version of symbols for SQL execution:

• stmt_execute_into_port
• sql_execute_into_port

Unlike the previous version, the results are stored in the port provided by the caller, rather then in the obuf. This avoids redundant data copying for the caller, who wants to return results "as is".

Ref:

• tarantool-module!581 (merged)
• tarantool-module!583 (merged)
• tarantool-module!585 (closed)