Add documentation and helpful links for downloading images

**Path to page with content (_do not_ include domain name):** https://bottlerocket.dev/en/os/1.14.x/install/

**What content is incorrect?** It only sort of covers how to use the quickstarts. But for metal, I have to work through https://github.com/bottlerocket-os/bottlerocket/blob/develop/PROVISIONING-METAL.md#fetch-the-bottlerocket-image-for-bare-metal which has a lot of steps, including installing Rust and compiling `tough` from source. This involves multiple steps when all I want to do is download the image and try it on my hardware. See https://github.com/bottlerocket-os/bottlerocket/discussions/2779 for a deeper discussion on how this could be improved.

**What should the content say or communicate?**
Ideally, I would like to see as simple as possible process to get an image on my local machine. Many Linux distros have download links for their images. A list of URLs for each variant and version where I could click the button and download the image would be easiest. I would probably want a SHA sum next to the URL provided so I could verify I got the right image and its intact once downloaded.

An alternative that would still make things a lot better would be to provide a pre-build binary of `tough` (to avoid having to install Rust and then compile `tough`) and the website provide the full invocation for `tough` so the "hard work" is done for me of figuring out things like "metal-k8s-1.27" is what I want for the url for variant or what the latest version is at that moment in time.

Start with the install page at /en/os/1.14.x/install/ and compare it with PROVISIONING-METAL.md, especially the image-fetching section. Document direct image URLs and SHA sums for the relevant variants and versions, or provide the complete tough invocation described by the issue. Check the linked discussion for context on the desired download flow.

Written by the indexing model from the issue text.