stop() shuts the socket down to end a request in flight, but on Windows
that does not wake a read waiting in WSAPoll (#1396). The request then
waited until the server answered, the read timeout passed, or the OS
dropped the connection.
stop() now also sets a flag, and send_() gives the request's stream an
interrupt check that reads it, as SSEClient::stop() does since 801bf2e.
The wait for data then ends within 100 ms on every platform. A request
started after stop() clears the flag. A redirect or a digest retry sent
inside the request keeps it.
select_read_interruptible() now rounds its last wait up to a whole
millisecond. poll() takes milliseconds, and the wait ended up to 1 ms
before the deadline, which MaxTimeoutTest caught once every client
request waited through this function.
* Add large data transfer test
* Replace `SSL_read` and `SSL_write` with `ex` functions
* Reflect review comment
* Fix return value of `SSLSocketStream::read/write`
* Fix return value in the case of `SSL_ERROR_ZERO_RETURN`
* Disable `LargeDataTransfer` test due to OoM in CI
Yoshiki Matsuda