Portable DID Doc's potentially out-of-date with networked Doc

Originally raised here https://github.com/TBD54566975/web5-rs/issues/211#issuecomment-2112689541 but creating a dedicated ticket here as this'll concern all SDKs. Copy pasting relevant comments:

> What happens in the following case:
>
> 1. Create a `did:dht`
> 2. Export it as a portable DID (which includes the DID Document)
> 3. Update the `did:dht` (as in, update the DID Document in the network)
> 4. At this point, what's in the portable DID's Document is different than the Document persisted in the network
> 5. Instantiate a bearer DID from the portable DID
> 6. At this point the developer has an out-of-date DID Document in their bearer DID instance
>
> I think we should consider removing the DID Document from the portable DID type and instead resolve upon each instantiation (upon each "import from a portable DID"). As I see it, if we want to create a dedicated type for portable DID's then that type should merely consist of:
>
> ```json
> {
> "uri": "did:dht...",
> "privateKeyJwks": [...]
> }
> ```

And then from @mistermoe

> aye we definitely chatted about this during the design phase of portable did. @frankhinek do you remember our rationale for choosing to include the did document as part of portable did?
>
> ah i think i remember. w.r.t. `did:dht` specifically, it may be the case that a did was _created_ but not _published_. if so, without including the did document in the portable did itself, fidelity is lost (e.g. on creation, _n_ `service`s were provided to `create`)
>
> This definitely doesn't negate the issue you've raised @KendallWeihe. The scenario you describe is entirely possible. At the time we decided that it was unlikely and felt that the furthest we should probably go (but didn't in any of the sdks) for the time being would be, on import, attempt to resolve. if resolution is successful, diff the portable did doc and the published did doc. if there's a difference, throw exception