Update all templates to use `template:_images/...` instead of `template://_images/...`

[jandubois]

Otherwise we get warnings from the bundled templates, e.g.

❯ l create template:fedora
WARN[0000] Template locator "template://_images/fedora-42" should be written "template:_images/fedora-42" since Lima v2.0
WARN[0000] Template locator "template://_default/mounts" should be written "template:_default/mounts" since Lima v2.0

We need to bump minimum Lima version when we do that:

minimumLimaVersion: 2.0.0