IntelliSense for language settings in settings.json

[jabacchetta]

It'd be useful to have IntelliSense for all language IDs when adding language-specific settings manually (as opposed to only showing IDs for those settings that already exist).

In other words, all language IDS that show up when using the Preferences: Configure Language Specific Settings command should also show up when manually adding those settings.

Notice in the screenshot that typescript is not available from the IntelliSense list, for example.

Language setting related issues: #58995 and #74195

[usernamehw]

Possible duplicate of #48317