Adding support for stack.ArrayStack in C++ backend

[nubol23]

Adds cpp backend for the stack implementation.

Based on Issue #511

Work in progress

[czgdp1807]

The segmentation was being thrown because the array types weren't registered in the stack extension module. So there are two options,

1. Register them manually (as I did in the above).
2. Import them at runtime via the APIs in https://docs.python.org/3/c-api/import.html.

For now approach in point 1 seems much easier and efficient because we pre-register everything that's going to be used in the module's implementation. So no need to import them during function calls. The second approach is messier as well (PyImport_Import every now and then whenever we want to use something from another C++ extension module).

[czgdp1807]

The following code works for me for example with 4b028f1 commit.

from pydatastructs.miscellaneous_data_structures._backend.cpp import _stack

array_stack = _stack.ArrayStack([1, 2, 3], int)

[czgdp1807]

In addition to #512 (comment) I removed calls to Py_INCREF/Py_XDECREF as they sometimes give segmentation faults. Anyways, avoid the calls to these two unless extremely necessary, like if your code only works after adding them at specific places then feel free to add otherwise ignore.

[czgdp1807]

Great progress @nubol23. I am glad that you are able to figure things out on your own in Python C-API. Let me know if you get stuck somewhere, we will fix the problem. :-)

[nubol23]

Thank you very much @czgdp1807 :) I added the remaining changes for the ArrayStack

[codecov]

Codecov Report

Merging #512 (4385edf) into master (3abc026) will increase coverage by 0.005%.
The diff coverage is 100.000%.

@@              Coverage Diff              @@
##            master      #512       +/-   ##
=============================================
+ Coverage   98.523%   98.528%   +0.005%     
=============================================
  Files           31        32        +1     
  Lines         3996      4010       +14     
=============================================
+ Hits          3937      3951       +14     
  Misses          59        59               

Impacted Files	Coverage Δ
...astructs/miscellaneous_data_structures/__init__.py	100.000% <ø> (ø)
...ructs/miscellaneous_data_structures/_extensions.py	100.000% <100.000%> (ø)
...datastructs/miscellaneous_data_structures/stack.py	100.000% <100.000%> (ø)

[czgdp1807]

Great job @nubol23. 🎉🎉