Support Inline StreamSends

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Description

Adds support for StreamSend calls that already happen on a callback to immediately flush inline, eliminating extra queuing delays (and sometimes eve additional packets sent on the wire).

One tricky piece here is the possibilities of additional callbacks as a result. For now, I've disabled when using send buffering because that very likely will complete the send immediately if it can be buffered.

Testing

CI/CD

Documentation

N/A

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This seems to be crashing the release build, kernel mode tests somehow. I think they somehow generate re-entrant callbacks, and are hitting our asserts. I'm going to turn this back to draft for now, and see if I can fix the latency issue with ACK tolerance.