Support VS Code settings in devfile

[phaumer]

Is your enhancement related to a problem? Please describe

When you start a workspace from the dashboard you provide a url to a git repository with a devfile.
When the workspace is created Che actually creates a multi-root workspace in which the repo specified in the dashboard is only one member.
As a result of being inside a multi-root workspace many of the settings provided in the repository's .vscode/settings.json are now ignored, because they need to be now specified in the .code-workspace file.
An example is the files.associations setting that is now being ignore making the workspace immediately unusable, when users depend on the custom file extensions, until they have manually copy-pasted the settings into the .code-workspace file. This makes standardization of tools and settings for a specific project difficult as users have to manually finish the setup.

Describe the solution you'd like

As the team really specifies a devfile when creating a repository that they want to load into workspaces, it would really make sense imho to allow specifying VS Code user settings as well as perhaps even the list of VS Code extensions to load inside the devfile. This could be similar to what you can do today in devcontainer.json files supported by VS Code Remote.

Describe alternatives you've considered

I know that you can achieve something similar with various config maps, but config maps are in the domain of the cluster admin and not the development team's domain, which is reponsible for the devfile, which is also repo specific. Doing things relevant for configuring a workspace with a specification that users of the same repo can share, should imho be done as much as possible in the devfile and not config maps as they are either personal only or require admin privileges for providing them to multiple users.

Additional context

See Slack discussion https://ecd-tools.slack.com/archives/C05SD64M85R/p1736302909277859

[vitaliy-guliy]

There is a workaround, if the repository root contains .code-workspace workspace file, this file will be used to define the workspace.
Try to create a workspace using this sample https://github.com/vitaliy-guliy/openshift_test/tree/with-code-workspace-file