3.8.0

• bump botocore dependency specification to support
  "botocore >= 1.43.3, < 1.43.47" (#1605, #1606, #1635, #1651, #1655)
• port botocore 1.43.24's long-polling no-retry signal
  (handler_response is False) through the async retry path so retries
  don't block the event loop with a synchronous sleep during backoff (#1606)
• fix AIOHTTPSession/HttpxSession blocking the event loop on the
  first request per proxy: SSL context creation (certificate loading via
  load_verify_locations/load_cert_chain) now runs in a thread via
  asyncio.to_thread instead of directly on the loop (closes #1469)
  (#1587)
• restructure StreamingBody to subclass botocore.response.StreamingBody
  (dropping the wrapt.ObjectProxy wrapper) and add full httpx API
  parity — read(amt), readinto(), readlines(), async iteration,
  iter_lines()/iter_chunks(), tell(), close() — where
  read(amt) previously raised ValueError; note that
  AioStreamingBody.__aenter__ now returns self instead of the raw
  aiohttp ClientResponse (use .raw_stream for the underlying
  response) (closes #1365) (#1539)