* ui: Remove custom css-vars 'polyfill' and use native CSS props
Previously we used a sort of polyfill for certain places where we needed
CSS property-like behavior. This meant duplicating code between JS and
CSS, specifically some of our SVG icons.
We moved to CSS props only in the places where they are beneficial and
populated the variables with our already existing SASS variables.
This means we no longer have to duplicate CSS and we can remove our
custom css-var helper/polyfill.
* Change all instances of yield/block-slots to use attributes over positional arguments
* Remove the ability to use yield/block-slots with positional params
This gives more prominence to 'Service Instances' as opposed to 'Services'. It also begins to surface Connect related 'nouns' such as 'Proxies' and 'Upstreams' and begins to interconnect them giving more visibility to operators.
Various smaller changes:
1. Move healthcheck-status component to healthcheck-output
2. Create a new healthcheck-status component for showing the number of
checks plus its icon
3. Create a new healthcheck-info component to group multiple statuses
plus a different view if there are no checks
4. Componentize tag-list
John Cowen