Fix pkg_mgr fact on OpenBSD (#30725)

* Fix pkg_mgr fact on OpenBSD

Add a OpenBSDPkgMgrFactCollector that hardcodes pkg_mgr
to 'openbsd_pkg'. The ansible collector will choose the
OpenBSD collector if the system is OpenBSD and the 'Generic'
one otherwise.

This removes PkgMgrFactCollectors depenency on the
'system' fact being in collected_facts, which also
avoids ordering issues (if the pkg mgr fact is collected
before the system fact...)

Fixes #30623

lib/ansible/module_utils/facts/system/pkg_mgr.py

@@ -50,20 +50,28 @@ PKG_MGRS = [{'path': '/usr/bin/yum', 'name': 'yum'},
             ]
 
 
+class OpenBSDPkgMgrFactCollector(BaseFactCollector):
+    name = 'pkg_mgr'
+    _fact_ids = set()
+    _platform = 'OpenBSD'
+
+    def collect(self, module=None, collected_facts=None):
+        facts_dict = {}
+
+        facts_dict['pkg_mgr'] = 'openbsd_pkg'
+        return facts_dict
+
+
 # the fact ends up being 'pkg_mgr' so stick with that naming/spelling
 class PkgMgrFactCollector(BaseFactCollector):
     name = 'pkg_mgr'
     _fact_ids = set()
+    _platform = 'Generic'
 
     def collect(self, module=None, collected_facts=None):
         facts_dict = {}
         collected_facts = collected_facts or {}
 
-        pkg_mgr_name = None
-        if collected_facts.get('system') == 'OpenBSD':
-            facts_dict['pkg_mgr'] = 'openbsd_pkg'
-            return facts_dict
-
         pkg_mgr_name = 'unknown'
         for pkg in PKG_MGRS:
             if os.path.exists(pkg['path']):