4.7.4

Fixed

• A connection attempt that outlives its timeout no longer terminates the pool,
  and with it every caller of that pool. The dial is made with the request's
  connect_timeout, and a call that times out, like a connection process that
  dies while dialing, comes back as a checkout error (#927, #928, thanks
  @aboroska).
• Handing a pooled connection to a new owner, and the prewarm dial, are guarded
  like the other calls the pool makes into a connection process. A connection
  that is gone or wedged is dropped instead of taking the pool down (#929).
• Stopping a connection from inside the pool is bounded to 100ms, after which
  the connection is killed. A connection wedged in a transport call, which a
  failed dial makes likely, used to hold every caller of the pool for as long
  as the transport took to return (#929).
• The health probes the pool runs on a connection (is_ready, checkin_info,
  set_owner, get_state) take an explicit timeout, and the pool passes
  250ms. h2_conn_usable/1 used the 5s default, so one wedged HTTP/2
  connection stalled the pool for 5 seconds on every checkout for that host
  (#929).

Added

• Fault injection test harness for the pool: a transport which can be told to
  misbehave, a sentinel which makes a dead pool visible, fault and chaos
  suites, and a structural test which fails if the pool calls a connection
  process outside a try. DEVELOPMENT.md explains how to use it (#929).

Changed

• Update dependencies to their latest releases: h2 0.12.0 and webtransport
  0.4.5 (#930).