Resolve module dependencies unless no_deps is specified
    
    By default, for a source_type of module, include the modules that a
    module requires as well as the module itself. This can be disabled
    with the no_deps flag. With or without no_deps the passed-in module
    list is validated not to contain duplicate modules with the same
    name but different streams or versions.
    
    For tests, add a @mock_pdc decorator that executes a function with
    PDC requests redirected to a local implementation that queries against
    a fixed array of (simplified) results.