Support Multiple DNS Resolution Connection Attempts

[nibanks]

Describe the feature you'd like supported

Currently, when MsQuic is given just a ServerName to connect to, is resolves that with DNS and takes the first address returned. Instead, MsQuic should support (not sure if it should be default behavior though) the ability to do "happy eyeballs" to try connecting to multiple/all IP addresses that were available.

Proposed solution

Generally, happy eyeballs would require multiple independent connections, but with QUIC, we might be able to cheat a little and use the same connection, but just different "path" objects. We could send the same client initial packet on to each server address, save the state in the path object, and just continue the rest of the connection with whichever path gets a response first.

This likely needs some design and/or prototyping work.