Changes GitHub Action OS Image to Avoid Python Caching Issues

[ilumsden]

This PR allows us to avoid this issue with the setup-python Action used in Hatchet's CI.

To do so, it simply changes the OS image for the CI from ubuntu-latest to ubuntu-20.04. When the linked issue is resolved, we can switch back to ubuntu-latest.

[ilumsden]

This PR will also upgrade the codecov Action used in the unit testing to v3. codecov-action v1 (which we were previously using) has been sunsetted and no longer works.

[ilumsden]

@slabasan this PR is now complete, pending a rebase. It now contains the following changes:

• Fixes the original issue with the setup-python action described in the first comment of the PR
• Changes .coveragerc so that all coverage files are saved into a .coverage/ subdirectory
• Upgrades codecov-action from v1 (which no longer works) to v3
• Adds several arguments to the invocation of codecov-action, namely:
  • verbose: enables verbose output from the action
  • env_vars: ensures the values of the runner's OS and PYTHON environment variables are included in the code coverage report
  • directory: ensures that the action looks in the correct place for the coverage files (i.e., the .coverage/ subdirectory)
• Changes np.float to np.float64 in the timemory_json_data function in conftest.py because np.float has been removed from newer versions of NumPy