Misc config loading fixes

The main motivation behind this is simplicity and correctnes, but the new small config library is also faster:

```
BenchmarkDefaultConfigProvider/Viper-16         	  252418	      4546 ns/op	    2720 B/op	      30 allocs/op
BenchmarkDefaultConfigProvider/Custom-16        	  450756	      2651 ns/op	    1008 B/op	       6 allocs/op
```

Fixes #8633
Fixes #8618
Fixes #8630
Updates #8591
Closes #6680
Closes #5192

output/outputFormat.go

@@ -368,7 +368,11 @@ func decode(mediaTypes media.Types, input interface{}, output *Format) error {
 		return err
 	}
 
-	return decoder.Decode(input)
+	if err = decoder.Decode(input); err != nil {
+		return errors.Wrap(err, "failed to decode output format configuration")
+	}
+
+	return nil
 
 }