refactor: try to refactor the load config coode to 2 clear pathes

[qs-wang]

• split loadConfigByProvider to a separate method to make if/else statement clearer
• split loadPrivateConfigFromFile to a separate method for reuse in if/else branches

I tried to make some changes for my own purpose. While I read the code although the code works perfectly, it a little bit hard to understand and change because the config loading logic from the provider and file are mixed. I refactored it to split the loading logic , i.e. loading from provider and file, to 2 methods, which made my changes easier. Later on I found other solution so the changes got dropped, but I am trying to push the refactor to see if anyone is interested.

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