Move image list to top level

[edlerd]

Done

• Move image list to top level
• rename cached image to images

QA

1. Run the LXD-UI:
   • On the demo server via the link posted by @webteam-app below. This is only available for PRs created by collaborators of the repo. Ask @lorumic or @edlerd for access.
   • With a local copy of this branch, run as described here.
2. Perform the following QA steps:
   • browse the image list form the top main menu
   • delete cached image
   • start new instance and ensure the image appears in cached images
   • check image list for another profile

[webteam-app]

Demo starting at https://lxd-ui-522.demos.haus

[piperdeck]

recalling a previous conversation, I approve of this change. I would like to do more work on the images page later on, but if this PR only concerns moving the page itself to the top-level navigation, then it looks good to me.

[lorumic]

Thanks for applying the changes!