Implement GH-8641: STREAM_NOTIFY_COMPLETED over HTTP never emitted

This adds support for the completed event. Since the read handler could
be entered twice towards the end of the stream

Implement GH-8641: STREAM_NOTIFY_COMPLETED over HTTP never emitted

This adds support for the completed event. Since the read handler could
be entered twice towards the end of the stream we remember what the eof
flag was before reading so we can emit the completed event when the flag
changes to true.

Closes GH-10505.

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