Release v1.6.6

What's Changed

• LCC & GCC on TopicCursor, move VectorClock into xmtp_proto by @insipx in #2878
• use SmallVec for Topic type by @insipx in #2879
• Make stream_message_deletions async by @rygine in #2890
• Make stream_message_deletions async (#2890) by @rygine in #2891
• Fix: Tester dev flag by @codabrink in #2892

Full Changelog: v1.6.4...v1.6.6