Gateway: support Host header

[lidel]

Gateway exposed by js-ipfs should check Host header and produce valid responses based on its value:

• DNSLink gateway Host: {domain-with-dnslink}
  DNSLink (http://dnslink.dev)
  This will enable js-ipfs to be used with regular domain names
• Subdomain Gateway Host: {cidv1b32}.ipfs.* and Host: {cidv1b32}.ipns.*
  Subdomain gateway (CID as a Subdomain in-web-browsers#89, Subdomain Gateway kubo#6498)
  This would also unlock HTTP Proxy mode described in Act as HTTP PROXY for http://<cidv1b32>.ipfs.localhost #1877

[lidel]

Prior art: go-ipfs implementation of subdomain gateways:

• https://github.com/ipfs/go-ipfs/blob/master/docs/config.md#gatewaypublicgateways

[whizzzkid]

js-ipfs is being deprecated in favor of Helia. You can #4336 and read the migration guide.

Please feel to reopen with any comments before 2023-06-05. We will do a final pass on reopened issues afterward (see #4336).

This might already be resolved in Helia, if not please feel free to create an issue there.