Support consuming https://badbits.dwebops.pub/badbits.deny

[lidel]

We want rainbow to be enough to do badbits handling at ipfs.io / dweb.link.
If it is good enough for us, it will be good enough for people who self-host.

Unfortunately, https://badbits.dwebops.pub/badbits.deny is not append-only (https://github.com/protocol/badbits.dwebops.pub/issues/32733), and HTTPSubscriber from nopfs assumes the list is. We also gave bug around CAR handling.

Below is a list of known issues that we need to close to make it a viable recommendation:

• denylist: ?format=car does not skip directly blocked CIDs kubo#10361
• HTTPSubscriber: detect when list is not append-only ipfs-shipyard/nopfs#39
• HTTPSubscriber: check with If-None-Match or If-Modified-Since ipfs-shipyard/nopfs#38
• Support legacy double-hash entries for IPNS CIDs and DNSLink ipfs-shipyard/nopfs#40