Use synchronize option to sync settings

[WilsonZiweiWang]

The synchronize option is marked as deprecated but what we did to sync the settings was not a good practice either. The recommended pull-model for configurations is demonstrated here. However, this model doesn't really fit our case as the logging level needs an immediate update but others can be fetched when needed.

One of the advantages of using the pull-model is it can specify the scope (user/workspace/workspaceFolder) of the configurations before fetching.