BUG/MINOR: h3: adjust error on PUSH_PROMISE frame reception

BUG/MINOR: h3: adjust error on PUSH_PROMISE frame reception

HTTP/3 PUSH_PROMISE frames are systematically rejected with H3 error
FRAME_UNEXPECTED. This is adapted on the server side as a client can
never emit them.

This patch adapts error reporting when haproxy runs as a client. In this
case, server is still forbidden to emit any PUSH_PROMISE as MAX_PUSH_ID
frames are never emitted. In this case, ID_ERROR must be used as an
error code.

This must be backported up to 3.3.