fix!: did bytes schema

[alanshaw]

This PR fixes the didBytes schema so that it returns the type it is designed to read - Uint8Array. Concretely this changes the return type from read to be a PrincipalView, which is a subclass of Uint8Array.

The issue is that while this schema (in its current form) can read and validate data encoded as a Uint8Array, you cannot create an invocation/delegation with a value of a Uint8Array - it expects a string DID:

Type 'Uint8Array<ArrayBufferLike>' is not assignable to type '`did:${string}:${string}` & `did:${string}` & Phantom<{ protocol: "did:"; }>'.

If you pass a string, it will be encoded as a string, which is not the value that can be read by the same schema.

In real terms, I'm trying to create a location claim with a byte encoded space DID but I cannot 😢

In hindsight, this schema type should perhaps be called principal. I'd be open to changing this PR to add that and deprecate didBytes instead if folks feel strongly.

[hannahhoward]

Lgtm and I prefer the rename to Principal if we have bandwidth to do it.