Provide links/artifacts for Bottlerocket images

Related to: https://github.com/bottlerocket-os/bottlerocket/discussions/2779

Potentially we could consider providing links to Bottlerocket image artifacts to make it easier for folks to directly download images.

Using TUF and `tuftool` provide some security guarantees via signature validation, etc. We need to carefully consider providing direct links that wouldn't give those same guarantees.

Start by reading the related Bottlerocket discussion and the issue's concerns about TUF and tuftool signature validation. Done means reaching a decision on whether direct image links can be provided without losing those security guarantees, and documenting the resulting approach for the website.

Written by the indexing model from the issue text.