Bring "attach config" devcontainer.json subset into spec

While not as full featured as the full devcontainer.json flow, the attach configuration flow is useful for scenarios where you already have a running container you want to interact with. To recap, this allows is a subset of devcontainer.json properties to be applied to an already running container. The idea is that tools "attach" to a container that were spun up in some way while still taking advantage of some of the capabilities that the metadata in the dev container spec enables. [The current list of properties can be found here](https://code.visualstudio.com/docs/remote/attach-container#_attached-container-configuration-reference) (tho some would move under `customizations` per #1).

This subset (`customizations` aside) could also represent the minimum bar for when something would be said to support the spec. These properties are also very compatible with the idea of using labels to store metadata (#18), particularly if this expanded to also support labels on containers in addition to images, so file-based representation would be only one form.

With this in mind, we could refer to this as a "minimal profile" of dev container properties (verses "full profile"). This subset of properties should also work with any orchestrator (related to #10) since they can all be applied at runtime which further highlights the value of bringing the idea into the spec. That said, despite naming, it likely makes sense to have a separate schema with this subset to aid use.

More complex capabilities like features would not part of this configuration, though should we move forward with label-based metadata (#18), there's no reason you couldn't pre-build an image, reference it, and then use this minimal profile for anything else that is needed.

Inizia esaminando le proprietà attuali di devcontainer.json nel riferimento di configurazione attach-container collegato, insieme alle discussioni in #1, #10 e #18. Definisci il profilo minimo proposto e i relativi limiti di schema separati, incluso ciò che viene escluso; il lavoro sarà considerato completato quando ci sarà accordo sul sottoinsieme di proprietà e su come si applica negli scenari attach e orchestrator.

Scritto dal modello di indicizzazione a partire dal testo della issue.