Migrate SE "New File" to command palette

[claudiaregio]

Describe the feature you'd like

Command: "Add New File" -> @Jxwoon Let's decide if we want the word template in here somehow

Unlike work done for #2194, it should ask which project they want to add the file to first, then show template list options

[github-actions]

@claudiaregio

A fix for this issue is now available in the next pre-releases of C#DK/C#. If you'd like to try out the fix, please see these instructions to update or try pre-release versions.