Add support for getting hardware facts on GNU Hurd (#18152)

* Fallback to /proc/mounts if /etc/mtab do not exist

On modern system, the file is just a compatibility symlink, and
some system (like GNU Hurd) do not have it, but provides /proc/mounts

* Add support for uptime, memory and mount facts on GNU Hurd

lib/ansible/module_utils/facts.py

@@ -1281,7 +1281,11 @@ class LinuxHardware(Hardware):
         return bind_mounts
 
     def _mtab_entries(self):
-        mtab = get_file_content('/etc/mtab', '')
+        mtab_file = '/etc/mtab'
+        if not os.path.exists(mtab_file):
+            mtab_file = '/proc/mounts'
+
+        mtab = get_file_content(mtab_file, '')
         mtab_entries = []
         for line in mtab.splitlines():
             fields = line.split()
@@ -2159,6 +2163,20 @@ class Darwin(Hardware):
         if rc == 0:
             self.facts['memfree_mb'] = int(out.splitlines()[-1].split()[1]) // 1024 // 1024
 
+class HurdHardware(LinuxHardware):
+    """
+    GNU Hurd specific subclass of Hardware. Define memory and mount facts
+    based on procfs compatibility translator mimicking the interface of 
+    the Linux kernel.
+    """
+
+    platform = 'GNU'
+
+    def populate(self):
+        self.get_uptime_facts()
+        self.get_memory_facts()
+        self.get_mount_facts()
+        return self.facts
 
 class Network(Facts):
     """