Server idle/read/write timeout support

On the server side, it's important to be able to clear out connections that have been idle for too long or are somehow broken. For HTTP/1, this can be done pretty simply by setting stream-level read and write timeouts. However, things aren't so simple for HTTP/2 since it's multiplexed. In particular, the server is always attempting to read from an HTTP/2 socket, so if a single request is active that takes more than the read timeout to process, the connection gets killed.

To handle this properly, I think we'll need hyper-level timeout configuration. In particular, I care about being able to shut down connections that have been idle for some period of time, and detect when reading from a client or writing to it is taking too long.

There are also some potential higher level timeouts to defend against e.g. slow loris attacks by placing a cap on the time a client is allowed to send the complete set of headers.

Start by tracing the server-side HTTP/1 and multiplexed HTTP/2 connection handling described in the issue, focusing on how reads, writes, and idle connections are currently managed. Define the timeout configuration and observable behavior for idle, read, write, and complete-header limits before implementing and validating it.