Deploy staging sites for all web projects

As agreed at the March 17th S9 meeting, the web team agreed to implement the same review/staging/production workflow across our different projects. This issue will track this progress.

Subdomains of staging.torproject.net will be created for this purpose. They will have a new static component in our web mirror system and an associated ssh private key will be added to each project's CI variables..

• blog.staging.torproject.net
• community.staging.torproject.net
• dev.staging.torproject.net (in development, not on static mirrors yet)
• donate.staging.torproject.net
• gettor.staging.torproject.net
• tb-manual.staging.torproject.net
• newsletter.staging.torproject.net
• research.staging.torproject.net
• status.staging.torproject.net
• styleguide.staging.torproject.net
• support.staging.torproject.net
• www.staging.torproject.net

Cleanup (vhost, docroots and LE configs):

• blog-staging.torproject.org
• support-staging.torproject.org
• www-staging.torproject.org