Add named supervisor credo check

[samuelmanzanera]

Description

This PR adds a credo check to ensure the supervisor are named and fix the un-named supervisors

Fixes #978

How Has This Been Tested?

Omit the commit ea098d3 and run mix credo.
It should report the supervisor which are not named.
After application of the same commit, the mix credo would not return errors.

Checklist:

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