Fixes #4142

- What I did
Added support for using mirrors to override default registry for specific registries or all registries

You will be able to do:

$ lkt --mirror http://mymirror.local      # to mirror all
$ lkt --mirror ghcr.io=http://mymirror.local      # to mirror just ghcr.io
$ lkt --mirror ghcr.io=http://mymirror.local/ghcr --mirror http://mymirror.local/other      # to mirror ghcr and rest differently

- How I did it
Added the CLI flag, then rewrite the URL

- How to verify it
CI

We probably should add a specific test for this, but I struggled to figure out how. Maybe I will get it

- Description for the changelog

mirror support