Domain name resolution does not handle RFC6761 special names correctly

[rzikm]

RFC 6761 Defines several DNS names to be handled specially by DNS resolution APIs and libraries:

• localhost, and *.localhost should always resolve to respective loopback address
• invalid and *.invalid should always resolve to NXDOMAIN response

Unfortunately, current OS-level resolution APIs on both Windows and Linux (I did not check MacOS, but I assume the situation is going to be identical to Linux) do not recognize subdomains of localhost or invalid as special, and forward the queries to the respective DNS server (which is against the RFC spec).

This feature would play well with dotnet/aspnetcore#62593, which introduces support for localhost subdomains was for local development.

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[filipnavara]

I did not check MacOS, but I assume the situation is going to be identical to Linux

We should check. The RFC was written by Apple employees so presumably they were standardizing something present in their implementation.

UPD: macOS Sequoia doesn't seem to handle it, tested with nslookup smoke test.

[BrennanConroy]

There was a follow-up change as *.localhost doesn't really work
dotnet/aspnetcore#62668