Improve settings UI for creating/deleting profiles

[meganrogge]

Should include a dropdown populated from the profileNames of the terminal.integrated.profiles.platform

[Tyriar]

Also proper controls for adding profiles would be cool

[Tyriar]

This is much more involved than anticipated, we basically need to create an "everything settings renderer" since there are no component-specific settings renderers by design, they're all general. So we'd need one that works with all the schema features profiles use (anyOf, inner env objects, etc.).

Closing this as we'll get it for free when it the settings ui feature is added.