fix: abort signal listening

[SgtPooki]

When adding #689, I had to make a change to verified-fetch (ipfs/helia-verified-fetch#214) that uses abortable-iterator when we walk a path, but we should be handling this better..

This issue is for addressing whatever fix where-ever we need to (probably @helia/verified-fetch and maybe some underlying libraries) so that we can revert the 214 pull request to verified-fetch.

The abort signal is not being listened to somewhere but I couldn't reproduce (https://github.com/SgtPooki/repro-helia-libp2p-router-abort-handling) except inside the service worker gateway.

Hopefully ipfs/helia#774 with ipfs/helia#776 will fix this, but I installed all the latest packages (@next) in service worker and still was unable to see a correct 504 like we have after making the change in ipfs/helia-verified-fetch#214

cc @achingbrain

Repro steps in this project:

1. install verified-fetch@2.6.5 and pin it
2. Run configurable timeout value is respected test with npm run test:chrome -- -g 'configurable timeout value is respected'

[SgtPooki]

Once ipfs/helia-delegated-routing-v1-http-api#166 and ipfs/helia-verified-fetch#223 are merged, this should be able to be closed.