Avoid "excessive message size" for session tickets

Avoid "excessive message size" for session tickets

We received a report of an "excessive message size" for a received
session ticket. Our maximum size was significantly less than the theoretical
maximum. The server may put any data it likes in the session ticket
including (for example) the full certificate chain so we should be able to
handle longer tickets. Update the value to the maximum allowed by the spec.

Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/15877)