* 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.
1. Addition of external source icons for services marked as such.
2. New %with-tooltip css component (wip)
3. New 'no healthcheck' icon as external sources might not have
healthchecks, also minus icon on node cards in the service detail view
4. If a service doesn't have healthchecks, we use the [Services] tabs as the
default instead of the [Health Checks] tab in the Service detail page.
5. `css-var` helper. The idea here is that it will eventually be
replaced with pure css custom properties instead of having to use JS. It
would be nice to be able to build the css variables into the JS at build
time (you'd probably still want to specify in config which variables you
wanted available in JS), but that's possible future work.
Lastly there is probably a tiny bit more testing edits here than usual,
I noticed that there was an area where the dynamic mocking wasn't
happening, it was just using the mocks from consul-api-double, the mocks
I was 'dynamically' setting happened to be the same as the ones in
consul-api-double. I've fixed this here also but it wasn't effecting
anything until actually made certain values dynamic.
