debian/control*: Update for fwupdate transition

Per Steve's recommendation:
 1. In fwupd, add Provides/Replaces, plus Conflicts: against the older
    versions of fwupdate-*-signed. That will tell apt to upgrade
    cleanly and thereby switch to fwupd instead. See
    https://www.debian.org/doc/manuals/developers-reference/ch05.html#s5.9.3