[C++][FlightSQL][ODBC][SQLPrimaryKeys] Implement SQLPrimaryKeys catalog function

[adarshvijayaraghavan]

Describe the enhancement requested

SQLPrimaryKeys is currently an unimplemented placeholder in the Arrow Flight SQL ODBC driver. In cpp/src/arrow/flight/sql/odbc/entry_points.cc, the entry point logs its arguments and then throws:

arrow::flight::sql::odbc::DriverException("SQLPrimaryKeysW is not implemented", "IM001")

The placeholder was added in #47725 with the intent that follow-up PRs would implement each API. This issue tracks implementing SQLPrimaryKeys.

The underlying capability already exists on the Flight SQL C++ client (cpp/src/arrow/flight/sql/client.h): GetPrimaryKeys() / GetPrimaryKeysSchema().

Ref (SQLPrimaryKeys spec): https://learn.microsoft.com/en-us/sql/odbc/reference/syntax/sqlprimarykeys-function

Parent issue: #30622

Component(s)

C++