Automate sync from dev.gitlab.org to GitLab.com after a security release

In a security release, we have the following items:

• Push ce/11-4-stable to all remotes
• Push ee/11-4-stable-ee to all remotes
• Push omnibus/11-4-stable and omnibus/11-4-stable-ee to all remotes
• Push CE, EE and omnibus tags to all remotes

Similar to the sync rake task in release-tools we could do this automatically. Perhaps:

/chatops run sync 11.4

The difference? It should only push relevant tags (perphaps via regex) to avoid pushing all the tags from dev to GitLab.com.

cc @rspeicher @marin @jprovaznik