Avoid app_handler Extra Jump to C++

[doctorlai-msrc]

This PR closes #51

The current implementation of the app_handler callback in Python apps contains unnecessary code that is causing performance issues and random Python crashes. This was done this way because we wanted to reuse the C++ code jrtc_app.cpp

The call chain is:

1. jrtc (C)
2. jrtc_pythonapp_loader.c (Python sub-interpreter)
3. jrtc_start_app (Python, user's code)
4. jrtc_app.py (C++ wrapper)
5. jrtc_app.cpp (C++)
6. app_handler (Python, user's code).

In the app_handler() function (user's code), the following (memory allocation) will crash the JRTC randomly:

a = 10000 * [0]
for i in range(10000):
    a[i] = 100 * [1]

This may be due to the memory allocation where the lists are allocated in the stack intead of the heap.

This PR implements the jrtc_app.cpp in Python, so the unnecessary hop to C++ space is eliminated. The jrtc_app.py will now be in Python instead of wrapping C++ code.

With this PR, the python app won't randomly crash for above Python code.

[matthewbalkwill]

I dont think the python apps should now have any references to ctypes, since this should now be python only

[doctorlai-msrc]

You can't have Python type here as AppStateVars is ctypes.Structures. Otherwise, this have to be moved out somewhere.

[matthewbalkwill]

but this doesnt need to be a ctypes.Strucutre does it ? It can be a simple Python dataclass, or even a dict

[doctorlai-msrc]

Fixed.

[matthewbalkwill]

As pre my previous comment, do we need any ctypes stuff here ? I think we just want to pass python varables