gh-106529: Support JUMP_BACKWARD in Tier 2 (uops) (#106543)

During superblock generation, a JUMP_BACKWARD instruction is translated to either a JUMP_TO_TOP micro-op (when the target of the jump is exactly the beginning of the superblock, closing the loop), or a SAVE_IP + EXIT_TRACE pair, when the jump goes elsewhere.

The new JUMP_TO_TOP instruction includes a CHECK_EVAL_BREAKER() call, so a closed loop can still be interrupted.

Python/ceval.c

@@ -2783,6 +2783,13 @@ _PyUopExecute(_PyExecutorObject *executor, _PyInterpreterFrame *frame, PyObject
                 break;
             }
 
+            case JUMP_TO_TOP:
+            {
+                pc = 0;
+                CHECK_EVAL_BREAKER();
+                break;
+            }
+
             case SAVE_IP:
             {
                 frame->prev_instr = ip_offset + oparg;