cfengine_stdlib.cf: Improve various rpm-based package_method bodies

This patch improves the package_method bodies "yum_rpm_enable_repo",
"rpm_filebased" and "generic" in the same way that the "yum_rpm" body
was recently improved:

  * Same list regexes as that of "yum" body
  * Support for specifying package arch
  * As a consequence of the above, package arch must be specified
    when removing packages in a multiatch environment, assuming e.g.
    both i386 and x86_64 versions of the package is installed

The "yum_rpm" body was similarly patched in commit 57074eb.