Fix a possible issue with comparing values with $null (#37763)

This PR includes:
- Fix $null comparison.
- Simplify Get-AnsibleParam in the same effort

lib/ansible/module_utils/powershell/Ansible.ModuleUtils.Legacy.psm1

@@ -201,11 +201,12 @@ Function Get-AnsibleParam($obj, $name, $default = $null, $resultobj = @{}, $fail
         }
     }
 
-    # If $value -eq $null, the parameter was unspecified by the user (deliberately or not)
+    # If $null -eq $value, the parameter was unspecified by the user (deliberately or not)
     # Please leave $null-values intact, modules need to know if a parameter was specified
-    # When $value is already an array, we cannot rely on the null check, as an empty list
-    # is seen as null in the check below
-    if ($null -ne $value -or $value -is [array]) {
+    if ($null -eq $value) {
+        return $null
+    }
+
     if ($type -eq "path") {
         # Expand environment variables on path-type
         $value = Expand-Environment($value)
@@ -249,7 +250,6 @@ Function Get-AnsibleParam($obj, $name, $default = $null, $resultobj = @{}, $fail
         # , is not a typo, forces it to return as a list when it is empty or only has 1 entry
         return ,$value
     }
-    }
 
     return $value
 }