Desired Version Negotiation Extension tests

[anrossi]

• Generate invalid Client VNE TP
  • ChosenVersion doesn't match Long Header (Add test for Chosen Version mismatch #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 (Add test for Chosen Version mismatch #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
• 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.