Use `internalId` for deserialisation of Cascade, ARIA tree, or outcomes

[Jym77]

• Using internalId to refer to DOM nodes, we should be able to deserialize an ARIA tree within the context of an existing DOM tree. For deserializing the DOM pointers, we'd just look up in the DOM tree and find the correct node.
• Cascade (rule trees) should be (de)serialisable in a similar way. May need internalId also for Style rules in the DOM.
• Outcomes of an audit could also be deserialized within the context of a "target bag" (DOM tree) to retrieve targets and of a rules set to retrieve rules (by URI).

We'd need to repopulate some of the caches upon deserialisation to avoid recomputing the same thing again when we try to access stuff...

This could open for faster rechecks in some places by not re-resolving cascade and ARIA, ... essentially allowing to freeze computation at some point, serialize it, and transport it somewhere (or somewhen) else before continuing.