Show a notice if a non-production site may be indexable by search engines

Creates an admin notice indicating the site may be indexable by search engines if blog_public option is 1

Additionally, the notice does not show if:

• the current user does not have manage_options
• the notice has been dismissed (saved in options, reset if blog_public is resaved to 1)
• the home url ends in .go-vip.co or .go-vip.net

https://github.com/Automattic/vip-go-mu-plugins/pull/1597