Desired Version Negotiation Extension tests

[anrossi]

• [ ] Generate invalid Client VNE TP
  • [ ] ChosenVersion doesn't match Long Header (#3123)
  • [ ] ChosenVersion not in OtherVersions list
  • [ ] ChosenVersion is zero
  • [ ] Zero version in OtherVersions list
  • [ ] ~~PreviousVersion = OriginalVersion~~ No longer in spec
  • [ ] ~~ReceivedVersions is wrong or empty (on Incompatible VN)~~ No longer in spec
• [ ] Generate invalid Server VNE TP
  • [ ] ChosenVersion doesn't match Long Header (#3123)
  • [ ] ~~OtherVersions list doesn't contain ChosenVersion~~ Allowed by spec.
  • [ ] ChosenVersion is zero
  • [ ] Zero version in OtherVersions list
• [ ] Server "upgrades" client to an incompatible version
• [ ] Known-answer-test for the Client and Server VNE TP
  • [ ] Variations on input version to ensure correct compatibility list
• [x] Refactor QuicVersionNegotiationExtEncodeVersionNegotiationInfo to write an encode/decode test

Copied from #1831

• [ ] Third party tries to force version downgrade via injected VN packet
• [ ] Third party changes the version field during handshake
• [ ] Server initiates incompatible version negotiation, and also does compatible version negotiation on the second attempt.