Refactor of stream_all_messages, fix flaky stream tests

[insipx]

• refactors stream_all_messages to return a impl Stream
  • Limits missed messages by draining old stream and using std::mem::replace
    • missed messages are still possible, but should occur much less frequently since the surface area went from the future of creating a new stream, to the time it takes to replace the stream with mem::replace.
  • the callback now just spawns a task which loops over the stream
• use tokio::sync::Notify to create formal sync points across streaming tests
• remove StreamCloser duplication and instead use tokio::task::JoinHandle as StreamCloser in ffi code
  • StreamCloser now has another end function, end_and_wait. end_and_wait waits for the stream to end before exiting the function. the end function is still fire-and-forget (allowing it to remain synchronous).
• stream functions are all uniformly synchronous which fixes the disparity between ffi & node. Stream functions return a StreamHandle that has async methods:
  • wait_for_ready: async waits until the stream is ready to accept messages
  • end_and_wait: ends the stream and waits for it to shutdown
• end is still sync and just tells the stream to stop without blocking
• new test for missed messages

fixes #772

Fixes most of the flaky tests, except for test_can_stream_group_messages_for_updates and test_can_stream_and_update_name_without_forking_group which are unrelated to the stream changes, and instead one of them suffers from the dblock issue (although only in CI), and the other is problematic I think b/c of publish_intents conflicts (also only in CI).

[richardhuaaa]

Well done, this is a number of very helpful improvements! TIL about tokio::sync::notify, that helps a lot with the flaky tests. And handling the changeover between streams more gracefully is very helpful for reducing missed messages.

I think we need to propagate some changes up to the mobile SDK's, now that the stream methods are synchronous?

[insipx]

I think we need to propagate some changes up to the mobile SDK's, now that the stream methods are synchronous?

Yeah there do need to be some minor sdk changes -- mostly from async to sync and one method has an error return removed