settings: resolve configuration settings

[GitMensch]

sadly vscode doesn't do this when querying the settings, so each extension has to do that on its own (microsoft/vscode#2809)

Please resolve ${config:name} when reading file/folder names like koverage.coverageFilePaths. In my setup there are multiple environment using the same code-workspace and the parts that are different per machine are setup for example in settings.my.folder which I can then use everywhere in tasks by ${config:my.folder} and ${env:HOME} "out of the box"; but for extensions this has to be manually resolved. Please do so.

Note a list of official namespaces and variables is available, this shows things like ${env:..}, ${workspaceFolder:..}, ${config:..}, ${userhome}.