Do read retries in quic hq-interop server

Do read retries in quic hq-interop server

Normally the throughput test in the interop harness requests several
hundred very small files, resulting in lots of small stream packets from
the client, which are nominally read in a single read operation (as they
typically fit into a single stream frame), and the server was written to
expect that.  However, its still possible, if a stream frame is packed
to the end of a datagram, that only part of its content is carried,
finished in a subsequent stream packet, which leads to a short read.

Augment the server to properly handle SSL_read transient failures so
that such an occurance is handled properly.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/26198)