Fix INSERT EXEC stale OID errors by closing target table before clearing context

During major version upgrade tests, BABEL-1944 was failing with could not
open relation with OID errors. The root cause was that error cleanup paths
were calling pltsql_clear_insert_exec_context() WITHOUT first calling
pltsql_insert_exec_close_target_table(), leaving insert_exec_target_rel_oid
set to a stale OID.

Fix: Add pltsql_insert_exec_close_target_table() calls before
pltsql_clear_insert_exec_context() in all error cleanup paths:
- iterative_exec.c: No TRY-CATCH cleanup path in !IsTransactionBlockActive
- iterative_exec.c: TRY-CATCH cleanup path in exec_stmt_iterative
- pl_exec-2.c: exec_stmt_try_catch cleanup

This ensures the target table OID is properly cleared and the lock is
released before the INSERT EXEC context is cleared.

Author: monk0707

contrib/babelfishpg_tsql/src/iterative_exec.c

@@ -1490,6 +1490,7 @@ dispatch_stmt_handle_error(PLtsql_execstate *estate,
 		edata = CopyErrorData();
 		error_mapped = get_tsql_error_code(edata, &last_error);
 		exec_set_error(estate, last_error, edata->sqlerrcode, !error_mapped);
+
 		if (internal_sp_started &&
 			before_lxid == MyProc->vxid.lxid &&
 			before_subtxn_id == GetCurrentSubTransactionId())
@@ -1544,6 +1545,7 @@ dispatch_stmt_handle_error(PLtsql_execstate *estate,
 					 * will be dropped by the transaction abort.
 					 */
 					elog(DEBUG1, "TSQL TXN TSQL semantics : INSERT EXEC active but no TRY-CATCH, clearing context for cleanup");
+					pltsql_insert_exec_close_target_table();
 					pltsql_clear_insert_exec_context();
 				}
 			}
@@ -1791,7 +1793,10 @@ exec_stmt_iterative(PLtsql_execstate *estate, ExecCodes *exec_codes, ExecConfig_
 
 						elog(DEBUG1, "INSERT-EXEC: Cleaning up after error caught by TRY-CATCH, temp_oid=%u", temp_oid);
 
-						/* Clear the INSERT EXEC context first */
+						/* Close target table and release lock first */
+						pltsql_insert_exec_close_target_table();
+						
+						/* Clear the INSERT EXEC context */
 						pltsql_clear_insert_exec_context();
 
 						/* Drop the temp table if it exists */

contrib/babelfishpg_tsql/src/pl_exec-2.c

@@ -2922,6 +2922,9 @@ exec_stmt_try_catch(PLtsql_execstate *estate, PLtsql_stmt_try_catch *stmt)
 			elog(LOG, "INSERT-EXEC TRY-CATCH cleanup: is_stmt_terminating=%d, insert_exec_was_active=%d, temp_oid=%u",
 				 is_stmt_terminating, insert_exec_was_active, temp_oid);
 
+			/* Close target table and release lock first */
+			pltsql_insert_exec_close_target_table();
+			
 			/* Clear the INSERT EXEC context */
 			pltsql_clear_insert_exec_context();