gh-107758: Improvements to lltrace feature (#107757)

- The `dump_stack()` method could call a `__repr__` method implemented in Python,
  causing (infinite) recursion.
  I rewrote it to only print out the values for some fundamental types (`int`, `str`, etc.);
  for everything else it just prints `<type_name @ 0xdeadbeef>`.

- The lltrace-like feature for uops wrote to `stderr`, while the one in `ceval.c` writes to `stdout`;
  I changed the uops to write to stdout as well.

Python/executor.c

@@ -41,7 +41,7 @@ _PyUopExecute(_PyExecutorObject *executor, _PyInterpreterFrame *frame, PyObject
         lltrace = *uop_debug - '0';  // TODO: Parse an int and all that
     }
     #define DPRINTF(level, ...) \
-        if (lltrace >= (level)) { fprintf(stderr, __VA_ARGS__); }
+        if (lltrace >= (level)) { printf(__VA_ARGS__); }
 #else
     #define DPRINTF(level, ...)
 #endif