GH-49482: [C++][FlightRPC][ODBC] Fix inconsistent SQLGetInfo values in global connection

[vanshaj2023]

What changed

• SQL_DDL_SCHEMA case now reads the boolean scalar to conditionally set SQL_DROP_SCHEMA and SQL_CREATE_SCHEMA to 0 when unsupported, instead of always writing non-zero values
• SQL_DDL_TABLE case applies the same pattern for SQL_DROP_TABLE and SQL_CREATE_TABLE
• SQL_CATALOG_AT_START changed to use SetDefaultIfMissing so it does not overwrite SQL_CATALOG_LOCATION already set by ARROW_SQL_CATALOG_TERM, eliminating an ordering-dependent conflict
• Removed per-test connect/disconnect workarounds and converted three tests from ConnectionInfoHandleTest back to ConnectionInfoTest

How to test

• Build ODBC tests and run TestSQLGetInfoCatalogLocation, TestSQLGetInfoDropSchema, TestSQLGetInfoDropTable with both mock server and global connection fixture
• All three tests should pass consistently regardless of connection reuse

Closes #49482

• GitHub Issue: [C++][FlightRPC][ODBC] Fix inconsistent values in SQLGetInfo in global connection #49482