This change adds a new configuration setting that sets the default
language mode of new untitled files created with Ctrl+N
(workbench.action.files.newUntitledFile).  This activates the user's
desired language mode when a new untitled file is created.

Fixes #8729.

Part of #16509

Due to issues #14151, #14149 & #14182

Make content update trigger after dirty status is evaluated

Save file even without file changes - so that Nodemon, Gulp, Chokidar and other file watchers restart (fixes #7470)