Support DNSLink resolution

All of this works only when IPFS Resolve Method is not Disabled and not Ask.

• DNSLink lookup works only for pages with 5xx response codes without a check for x-ipfs-path header and according to the IPFS Resolve Method settings above

How DNSLink lookup works:

• it looks for a DNS TXT record of next format dnslink=[value] for _dnslink.[hostname] domain. It should meet current dns preferences and use DoH and Secure DNS according to the settings. DNS requests should be cached and work without sending second requests to DNS servers for same hostname.
• If the lookup is successful and the dnslink is present it shows the Open in IPFS button in location bar, the button navigates to ipns://[hostname]

For pages with other response codes we check for x-ipfs-path header in response and according to the IPFS Resolve Method settings we show the Open in IPFS button in location bar without lookups, the button navigates to ipns://[hostname]

We should not show the botton for IPFS Gateway urls.

Example TXT record: dnslink=/ipfs/<CID for your content here>

[bbondy]

@diracdeltas @spylogsster @lidel how about so we can make progress here we limit to only when an IPFS selection is made away from Ask and not Disable. I.e. only for Gateway and Local options. We can discuss what to do with Ask in a different issue.

[jessicaschilling]

Love it! Small nit: would Open with IPFS or Open using IPFS be more accurate?