[DEE-171] Document the structure of the return value of checks in their docstring

[noamzbr]

Is your feature request related to a problem? Please describe.
Check parameters are well documented in the declaration of each check, but the structure of the return is either not documented for vision checks, or documented in run_logic() (which is inaccessible by users) for tabular checks

Describe the solution you'd like
Document the structure of the return value right below the parameter documentation, in the check declaration.

_DEE-171