nodejs.prov: find namespaced bundled dependencies
    
    The previous behaviour assumed that in a bundled package path,
    there is always `node_modules` directory on each other spot – i.e.:
    
    npm/node_modules/<dep1>/node_modules/<subdep>
        ^                   ^
    
    With namespaced bundled packages, this is no longer necessary the truth:
    
    npm/node_modules/@nmcli/<dep1>/node_modules/…
        ^                   ! – expected node_modules
    
    ---
    
    The previous implementation considered any directory not named
    `node_modules` as a package directory, and tried to process it as such.
    Among other things, it pruned the list of subdirectories to be processed
    to just another `node_modules` subdir, if that existed.
    With namespaced packages, this pruning in essence happened too soon,
    and so they were skipped altogether.
    
    With this patch applied, only directories that directly contain
    the `package.json` file are processed as package directories,
    meaning that the walk should correctly descend into namespaces
    (even nested ones, if they appear).
    
    Resolves: rhbz#2029904