* ui: Loader amends/improvements
1. Create a JS compatible template only 'glimmer' component so we can
use it with or without glimmer.
2. Add a set of `rose` colors.
3. Animate the brand loader to keep it centered when the side
navigation appears.
4. Tweak the color of Consul::Loader to use a 'rose' color.
5. Move everything loader related to the `app/components/` folder and
add docs.
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