MINOR: server: support QUIC for dynamic servers

MINOR: server: support QUIC for dynamic servers

To properly support QUIC for dynamic servers, it is required to extend
add server CLI handler :
* ensure conformity between server address and proto
* automatically set proto to QUIC if not specified
* prepare_srv callback must be called to initialize required SSL context

Prior to this patch, crashes may occur when trying to use QUIC with
dynamic servers.

Also, destroy_srv callback must be called when a dynamic server is
deallocated. This ensures that there is no memory leak due to SSL
context.

No need to backport.