Add GlBanner as ViewComponent

What does this MR do and why?

Adds a view component compatible with GlBanner and replaces two pure-Haml banners with it.

Implements #362616 (closed) and #362759 (closed).

Screenshots or screen recordings

AutoDevOps promotion:

Before	After

BurndownChart promotion:

Before	After

How to set up and validate locally

AutoDevOps promotion:

• Make sure you disable the "Default to Auto DevOps pipeline for all projects" setting in Admin / Settings / CI/CD.
• Make sure you don't have the "auto_devops_settings_dismissed" cookie set.
• Go to a new project. This should show the banner. If not, check the other conditions in show_auto_devops_callout? helper method.
• Close the banner. Reload the page. It shouldn't show up again 🍪

BurndownChart promotion:

• Make sure you don't have the "promote_burndown_charts_dismissed" cookie set.
• Go to any EE milestone. For me first milestone in the /milestones list worked.
• If it doesn't, check show_burndown_charts_promotion? method.
• Close the banner, reload. Gone?

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.