**API**: Avoid compose ID parsing in productmd classes
    
    So I've done some research over the last few days and come to
    the conclusion that the compose ID parsing code I wrote for
    fedfind is a lot more fragile and specific to Fedora's current
    use cases than I thought it was. It certainly won't work right
    for many RHEL cases. So to keep the productmd classes truly
    generic, let's have `ProductmdComposeResult` take the full
    composeinfo metadata dict as its input, not a compose ID as
    before. This is, of course, an API change.
    
    The Fedora classes still take a compose ID, but now find the
    release from it and pass the full metadata dict to the parent
    class. This is OK for current Fedora usage, and I intend to try
    and robustify the compose ID parsing in fedfind as much as I
    can with my new knowledge of productmd's behaviour, and restrict
    it to just discovering info we need to find the release from the
    CID.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>