Adds `pytest-cov`

[parshvadaftari]

Description

Integrates pytest-cov for tests converage.

Fixes #2542

Type of change

Please delete options that are not relevant.

• [x] New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Please delete options that are not relevant.

• [ ] Unit Test
• [ ] Test Script (please provide)

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] Any dependent changes have been merged and published in downstream modules
• [x] I have checked my code and corrected any misspellings

Maintainer Checklist

• [x] closes #2542]
• [x] Made sure Checks passed

[parshvadaftari]

@Dev-Khant @deshraj Can you review this?