fix: only traverse relevant part of HAMT

[aschmahmann]

Description

Switched the UnixFS resolver code to do resolve only the relevant part of a HAMT rather than potentially enumerating all of it.

Fixes: ipfs-shipyard/helia-service-worker-gateway#18

Notes & open questions

Change checklist

• [x] I have performed a self-review of my own code
• [x] I have made corresponding changes to the documentation if necessary (this includes comments as well)
• [ ] I have added tests that prove my fix is effective or that my feature works

[achingbrain]

I have opened a PR that uses the unixfs-exporter to traverse the DAG here - https://github.com/ipfs/helia/pull/455

It should also solve the issue reported in https://github.com/ipfs-shipyard/helia-service-worker-gateway/issues/18

[SgtPooki]

Closing in favor of #455