gh-144316: Fix missing exception in _remote_debugging with debug=False

[taegyunkim]

1. Adds missing PyErr_NoMemory() call when PyMem_RawMalloc() returned NULL.
2. Adds missing PyErr_Format() calls before calling set_exception_cause macro
3. Modifies set_exception_cause macro to assert an error is set.

• Issue: RemoteUnwinder.get_stack_trace is missing exceptions on some error code paths #144316

[pablogsal]

This macro is intended to add context to an exception not to be the actual cause of the error. Doing this will mask actual bugs in the code where we are not setting exceptions properly in places that should catch it and fail. Unfortunately this is not only is a partial fix but it will hide errors. The correct solution is finding the error paths that are not properly handling errors and fix there (and perhaps chain).

[taegyunkim]

@pablogsal Found PyMem_RawMalloc() call which didn't set PyErr when it returned NULL. Let me know if the changes to the macro look unnecessary.

[picnixz]

I think we should instead add assert(PyErr_Occurred()) in _set_debug_exception_cause instead.