Upgrade to latest `ipld-dag-cbor`

[mikeal]

We made a pretty big change to the ipld-dag-cbor API.

Instead of using {"/": baseEncodedString} to express links we're just using CID instances.

This will probably end up simplifying a bunch of code in js-ipfs but it will be a pretty impactful change. For encoding, we still support the old form, so you only need to move to the new way once you find it necessary. But, there's a breaking change on the decoder side because all links are now CID instances.

The direct ipld-dag-cbor dep is barely used, it's mostly used by deps of deps:

├─┬ interface-ipfs-core@0.78.0
│ └── ipld-dag-cbor@0.12.1
├─┬ ipfs-api@24.0.2
│ └── ipld-dag-cbor@0.12.1
├─┬ ipfsd-ctl@0.39.2
│ └─┬ ipfs-api@23.0.0
│   └── ipld-dag-cbor@0.12.1
├─┬ ipld@0.17.3
│ └── ipld-dag-cbor@0.12.1
└── ipld-dag-cbor@0.21.1

What's the best strategy for getting all the deps of the deps updated and into a release?

We don't want to release "ProtoSchool 1.0" until this changes is in a js-ipfs release. Link creation w/ ipfs.dag.put in IPFS is a big part of the basic tutorials and the new API is much nicer and easier to teach and we'd hate to teach people the old API and then change it a month later. But this also means that this dep upgrade will end up being a blocker for ProtoSchool if it lingers for too long.

[vmx]

I'm currently working on it. It seems easier than I thought, only flaky tests make it a bit harder.

[alanshaw]

The direct dependency on ipld-dag-cbor was removed in #1626 and IPLD was upgraded to a version including the breaking API changes here #1668. This will be in the upcoming js-ipfs 0.33 release.