YUM4/DNF compatibility via yum action plugin (#44322)

* YUM4/DNF compatibility via yum action plugin

DNF does not natively support allow_downgrade as an option, instead
that is always the default (not configurable by the administrator)
so it had to be implemented

 - Fixed group actions in check mode to report correct changed state
 - Better error handling for depsolve and transaction errors in DNF
 - Fixed group action idempotent transactions
 - Add use_backend to yum module/action plugin
 - Fix dnf handling of autoremove (didn't used to work nor had a
   default value specified, now does work and matches default
   behavior of yum)
 - Enable installroot tests for yum4(dnf) integration testing, dnf
   backend now supports that
 - Switch from zip to bc for certain package install/remove test
   cases in yum integration tests. The dnf depsolver downgrades
   python when you uninstall zip which alters the test environment
   and we have no control over that.
 - Add changelog fragment
 - Return a pkg_mgr fact if it was not previously set.

test/integration/targets/dnf/tasks/dnf.yml

@@ -301,6 +301,11 @@
         - "'changed' in dnf_result"
         - "'msg' in dnf_result"
 
+- name: verify that bc is not installed
+  dnf:
+    name: bc
+    state: absent
+
 - name: install the group again but also with a package that is not yet installed
   dnf:
     name:

test/integration/targets/dnf/tasks/repo.yml

@@ -87,6 +87,7 @@
       dnf:
         name: "{{ repodir }}/foo-1.0-1.{{ ansible_architecture }}.rpm"
         state: present
+        allow_downgrade: True
       register: dnf_result
 
     - name: Check foo with rpm