Ensure exit_json returns failed = False

This is required for modules that may return a non-zero `rc` value for a
successful run, similar to #24865 for Windows fixing **win_chocolatey**.

We also disable the dependency on `rc` value only, even if `failed` was
set.

Adapted unit and integration tests to the new scheme.
Updated raw, shell, script, expect to take `rc` into account.

lib/ansible/module_utils/powershell.ps1

@@ -62,6 +62,10 @@ Function Exit-Json($obj)
         $obj = @{ }
     }
 
+    if (-not $obj.ContainsKey('changed')) {
+        Set-Attr $obj "changed" $false
+    }
+
     echo $obj | ConvertTo-Json -Compress -Depth 99
     Exit
 }
@@ -88,6 +92,10 @@ Function Fail-Json($obj, $message = $null)
     Set-Attr $obj "msg" $message
     Set-Attr $obj "failed" $true
 
+    if (-not $obj.ContainsKey('changed')) {
+        Set-Attr $obj "changed" $false
+    }
+
     echo $obj | ConvertTo-Json -Compress -Depth 99
     Exit 1
 }