Bug 1704570 - Add memory reporting for MapObject / SetObject data. r=nbp

This change converts some heap-unclassified memory to js-content. These show
up in DMD reports now that Set/Map are used in the browser itself.

As a side-effect, this adds more precise tracking to UBI system for tenured
objects. The nursery objects don't have the expected size but this is
pre-existing similar to typed objects. Due to this mismatch it is difficult
to write automated tests for this.

Also mark the Map / Set types as using delayed metadata notification so that
reserved slots can be fully initialized before debugger is notified. This
only delays things to a few function calls later.

Depends on D111753

Differential Revision: https://phabricator.services.mozilla.com/D111754