Tests for /ipns paths and Cache-Control HTTP header

[hacdias]

This updates the conformance tests to bring them in line with the changes on the following PRs:

• gateway: clean Cache-Control and Last-Modified specs#436
• feat!: namesys refactor, ipns TTL bubbled up to gateway boxo#459
• refactor: namesys cleanup, gateway /ipns/ ttl kubo#10115

Currently, we are not allowing Cache-Control headers in /ipns paths, but that's about to change.

[github-actions]

Results against Kubo latest:
(check the action's summary for the full results)

Summary

Tests	Failures	Errors	Skipped
2045	0	0	0

[github-actions]

Results against Kubo master:
(check the action's summary for the full results)

Summary

Tests	Failures	Errors	Skipped
2046	0	0	0

[github-actions]

Results against Kubo ns-cleanup:
(check the action's summary for the full results)

Summary

Tests	Failures	Errors	Skipped
2046	0	0	0

[hacdias]

@lidel since the specifications say SHOULD all the time regarding Cache-Control and Last-Modified, I find it hard to write meaningful tests. For Cache-Control, I changed from "must not have" to "either is empty, or is public, max-age=*". Regarding Last-Modified, I simply did not add checks. The spec says it should be the resolution time. So that means it can either be set or not. The only thing I could do is checking if the date is valid if present, but that seems very meta into HTTP.

[lidel]

Ack, I think this is sensible for now. We will refine once DNSLink side of things is tackled in the future PRs.

[hacdias]

As this needs to be merged, and published before merging the Boxo and Kubo PRs, I am going ahead and merge this once CI completes (just removed the Boxo branch).