Fix circular imports

Motivation

As a hash core developer, I need to ensure to follow best practices of python modules and packages to make it easier for other developers to contribute.

Current state

We have the circular import problem in many cases such as running pytests on resources/test_download.py file only.

Desired state

We solved the previous error with resources.py and also refactored all of or import structure to become better manageable.

Steps

• Read online about circular imports
• Change the code so we get rid of them and have a clear plan for adding more imports.