Default formatter selection should write to project specific settings rather than global.

The new Default formatter selection feature, while handy, is unusable for it's stated usecase.

From the updates page "Many of our users work on different projects and often different projects use different document formatters." Right now, the quick pick will write to the user settings.json, which means every project the particular user works on will share a formatter, and to use it for the usecase of different projects using different formatters you would have to manually move it to the project local .vscode/settings.json directory.

It should also do this for workspace specific settings.