ceilometer 18.0.0 release

meta:version: 18.0.0
meta:diff-start: 17.0.0
meta:series: yoga
meta:release-type: release
meta:pypi: no
meta:first: yes
meta:release:Author: Előd Illés <elod.illes@est.tech>
meta:release:Commit: Előd Illés <elod.illes@est.tech>
meta:release:Change-Id: I3516aa1f6a236f4415f3e1c3373059b73efa2c04
meta:release:Code-Review+1: Goutham Pacha Ravi <gouthampravi@gmail.com>
meta:release:Code-Review+1: Matthias Runge <mrunge@redhat.com>
meta:release:Code-Review+1: Ghanshyam <gmann@ghanshyammann.com>
meta:release:Code-Review+1: wu.chunyang <wuchunyang@yovole.com>
meta:release:Code-Review+1: zhurong <aaronzhu1121@gmail.com>
meta:release:Code-Review+1: Rajat Dhasmana <rajatdhasmana@gmail.com>
meta:release:Code-Review+2: Thierry Carrez <thierry@openstack.org>
meta:release:Code-Review+2: Elod Illes <elod.illes@est.tech>
meta:release:Workflow+1: Elod Illes <elod.illes@est.tech>
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