Dedicated CE to EE Upgrade Page

We should have a dedicated page for people who would like to upgrade from CE to EE, located at /upgrade.

• It should follow the same design language as /installation, and offer options to view the upgrade instructions for the variety of installation methods we have.
  • Omnibus, Helm Charts, cloud images, source, etc.
• Towards the bottom, we can have a link back to /update for people who accidentally end up in the wrong spot.

We can iterate on the text, but I think the general format could look like this:

When an item has been expanded, we need three sections:

1. Backup
2. Upgrade
3. Enter License

The instructions should be able to be configureable for each item, like we support with our /installation page.