Emit user-defined groups as group(_)

[Scott-Guest]

Fixes #3439.

Whenever emitting attributes (to JSON, KORE, etc.), emit user-defined groups as [group(my-att-1, my-att-2)] even though the front-end internally represents them as [my-att-1, my-att-2].

This prevents user-defined groups from conflicting with internal attributes.

[Scott-Guest]

Blocked on #2625

If there is some built-in attribute my-att unintentionally missing from the whitelist, then this change will cause it to be emitted to KORE as \group{}("my-att"), breaking anything downstream depending on my-att.

To be safe then, we should wait until the whitelist is complete and the option to opt-out is removed before merging this.