Code Insights: Non UI final tweaks around the cloud landing page

Created by: vovakulikov

Desings Figma

Background

This is basically a follow up for the https://github.com/sourcegraph/sourcegraph/pull/31177

Things that are left from the cloud LP implementations at the moment.

• Add promo video
• Add gif (hero image) for the first section
• Add pings
• Make sure that pings from the in-product landing page and cloud landing page work independently
• One more added by @joelkw : https://github.com/sourcegraph/sourcegraph/issues/31686
• Merge this issue PR and close this issue when code insights GA will happen.