⚡️ Implement xdist for parallel testing

[tabaktoni]

Development related changes

Introduce parallel testing for local development or SSH machine split testing
poetry run pytest -v -n auto --dist loadscope test/

You can specify n number of workers that will execute the test.
-n auto

My machine is a Dual-Core Intel Core i5 so -n auto will set a number of workers based on a number of cores to 2.
However, based on my test I get the best performance when set -n 4 so each core deal with two workers.

• ⚡️ local test from 30+ min -> 19 min (Dual-Core Intel Core i5)
• package added pytest-xdist

Checklist:

• No linter errors
• Performed a self-review of the code
• Rebased to the last commit of the target branch (or merged it into my branch)
• Documented the changes
• Linked the issues which this PR resolves
• Updated the tests
• All tests are passing