Max concurrent stream improvements

[lovelydinosaur]

Right, there was some stuff I didn't quite get correct in #89

Absurdly I'd forgotten to use http2=True in my testings. This is the script I'm using now for this...

importasyncioimporthttpcoreasyncdefmain():
asyncwithhttpcore.AsyncConnectionPool(http2=True) asclient:
awaitasyncio.gather(*[request(client, idx) foridxinrange(1000)])
asyncdefrequest(client, idx):
http_version, status_code, reason_phrase, headers, stream=awaitclient.request(
method=b'GET',
url=(b'https', b'example.org', 443, b'/'),
headers=[(b'host', b'example.org:443')]
)
try:
body=b''.join([chunkasyncforchunkinstream])
finally:
awaitstream.aclose()
asyncio.run(main())

The changes here are:

• We need to use the local settings to determine how many concurrent streams we can issue, not the remote settings.
• The stream_id = self.h2_state.get_next_available_stream_id() needs to be part of the semaphore-limited wrapped code, or else it stops incrementing once we've hit the concurrency limit. As a result I've moved the wrapping layer out from AsyncHTTP2Stream onto AsyncHTTP2Connection instead.

[yeraydiazdiaz]

Nice! 👍