CE port Resolve "Promote starting a GitLab.com trial"

See merge request gitlab-org/gitlab-ce!21551

(cherry picked from commit f90fc922)

693e435f port EE
76980873 fix gcp signup offer close js class
f8e74da7 Review changes
1ea69589 Update user_has_namespace_with_gold? to check for any plan instead of just gold plan
76bc9eef Fix dismissable_callout import
8c4399e5 Lint
aee0abc8 Use initDismissableCallout for trial callout
2ab3e57c Update clusters/_banner
c58a4ea8 Lint
086549d9 fix cherry picking
05afd11e Merge remote-tracking branch 'origin/master' into ce-6983-promote-starting-a-gitlab-com-trial
ba2ad0f0 fix persistent_user_callout import
9f5a7e2d Update dismissable_callout.js to correct missing import path slash
45613341 Remove dismissable_callout as it has become an unneeded wrapper for persistent_user_callout
df3f369f Merge branch 'ce-6983-promote-starting-a-gitlab-com-trial' of…
1b16ef30 mainta...