CNCF page

Created by: attfarhan

Addresses https://github.com/sourcegraph/sourcegraph/issues/14318.

We want to add a community page for Sourcegraph/cncf. This searches over the repogroup cncf.

• Include all CNCF projects in repogroup:cncf commit
• Add CNCF repogroup on the Sourcegraph.com homepage (bump to first repogroup)
• This opens to a clean homepage (http://sourcegraph.com/cncf) with - CNCF logo - a title right below (Search the 67 CNCF projects -> linking to the list of projects). Note this looks like a clean homepage (don't show Example searches or any other sections below the search bar)
• In the Search bar, omit 'repogroup:', it's fine that repogroup: will appear when you go to the search results page
• Remove everything from the top navbar (preferable both when signed it or not) - campaigns, extensions, code insights (only visible if feature flag is enabled), etc.
• Any code host, browser extensions, etc. toasts and notifications are removed. Is there anything else obtrusive we can remove?

Out of scope for this PR:

• Remove the cookie notice (needs to happen in cookiebot)
• Set up opsgenie monitoring and logging for usage => https://github.com/sourcegraph/deploy-sourcegraph-dot-com/pull/3562
• LSIF code-intel for as many repos as possible (mostly Go?)
• User test this!
• Ensure CNCF repositories are cloned and indexed