Backport rpmautospec fallback macros
    
    rpmautospec koji plugin bakes in the result of %autorelease and
    %autochangelog into the SRPM. When used on a Fedora or EL 9 machine with
    rpmautospec installed, fedpkg does the same. However, it's currently
    impossible to rebuild specfiles that use rpmautospec on EL 8 itself due
    to the unexpanded %autorelease and %autochangelog macros failing the
    SRPM build.
    
    This adds the same fallback %autorelease and %autochangelog macro
    definitions that are available in the Fedora and EPEL 9 buildroots. This
    allows locally rebuilding packages that use rpmautospec with plain
    rpmbuild or fedpkg on an EL 8 system or with `mock --spec`.