refactor: use gateway from go-libipfs

[hacdias]

Part of #8524

This PR is tracking my efforts to isolate the Gateway into a sub-package which will be key to solve #8524. The plan is to first isolate the gateway inside a sub-package that does not depend on anything else from Kubo. After, we can extract it to go-lipipfs.

Progress:

• Isolate handlers
• Remove dependencies on:
  • kubo/tracing package - might be harder, we may want to instead extract this as a module too.
    • I extracted tracing.Span into spanTrace inside the gateway subpackage. I think this should be fine as we will still be able to continue to use the tracing functionalities.
  • kubo/assets package
    • I also improved the assets package and remove the dependency for NPM. NPM was simply running a few shell scripts which were now simplified under the build.sh file. In addition, I updated the testing script to help visualize both the DAG and the Directory indexes, as well as improved the README.
• Move all unit tests (as possible) that are gateway specific to gateway
• Add a README.md with an example of how it can be run 😃

TODO:

• Merge and release Extract Gateway Code From Kubo boxo#65
• Update dependency here and rebase
• Merge

cc @lidel for visibility

[hacdias]

@lidel I think I have achieved a very good result here. Everything gateway related is completely extracted into the gateway sub-package. I made sure that the gateway package does not depend in any other part of the Kubo base code. You can see my initial comment about it. In addition, I slightly refactored the gateway assets in order to make them easier to work with. I'm happy to receive feedback on this and address it.

We may, or not, merge this PR into Kubo's basecode. Once IPNS is merged to master, I will be rebasing this PR. Then, we can either merge this in Kubo and only then perform extraction. Or, I can use this branch as the base for the extraction. it doesn't matter. Either way, this PR allows you to see how the isolated gateway code will look like.

CI: the CI is a bit flaky for unknown reasons to me. In addition the CodeQL CI thingy is flagging things that were already here, but since they were moved, it now thinks they are new issues.

[lidel]

@hacdias IPNS PRs are in master (#9399, #9471) – feel free to rebase and make any changes to make this ready for final review 🙏

[hacdias]

@lidel I opened a PR in go-libipfs to add the gateway code there: ipfs/boxo#65

Also updated here to use go-libipfs instead.

[hacdias]

@lidel interop is failing bc Cloudflare npm 524.

[lidel]

💭 Let's park merging this until #9579 ships, so it is easier to compare branches. I'll review a bit later.

[lidel]

Reviewed and merged ipfs/boxo#65, this one looks good too.

We should merge this asap so we don't get PRs against old gateway code in this repo.
Ok to open a separate one for GO interface adjustments described in ipfs/boxo#61

@hacdias feel free to switch this PR to the revision from main branch there and merge 🙏