sysutils/graylog: update to 2.4.6

• use templating to manage graylog_logging.xml config
• update mentioned dependencies in pkg-message.in
• update server.conf from 2.4.6 source extract
• re-import FreeBSD ports variables into server.conf.in

PR: 233181
Submitted by: dch
Approved by: thomas@bartelmess.io (maintainer timeout)
Sponsored by: Netzkommune GmbH
Differential Revision: https://reviews.freebsd.org/D17965