[unit-test] Correct commented unit tests to take them back

In pull request https://github.com/sealerio/sealer/pull/1476, we have succeeded in making unit-test work. While after that pull request, we found that we have very few unit test coverage, and this will definitely lead to the poor quality of sealer.

So I think we should try to gradually add all those commented unit tests back.

And we encourage the all community participants could feel free to help and contribute.

The example comment test case is like :

https://github.com/sealerio/sealer/blob/main/build/layerutils/charts/charts_test.go#L17-L47

https://github.com/sealerio/sealer/blob/main/pkg/config/config_test.go#L24-L106

and so on.