connection bookkeeping on the pool changes, where all conections are kept around, even the ones that close during the scope of the requests; new requests may then find them, reset them, an reselect them. this is a major improvement, as objects get more reused, so less gc and object movement. this also changes the way pool terminates, as connections nonw follow a termination protocol, instead of just closing (which they can while scope is open)
first attempt at more granular error handling: during response chunk processing, errors will be handled in a way where current response stops being fetched; for http/1, the connection is fully reset, for http/2, the individual stream is cancelled
