ui: Fix using 'ui-like' KVs when using an empty default nspace

[johncowen]

When using namespaces, the 'default' namespace is a little special in
that we wanted the option for all our URLs to stay the same when using
namespaces if you are using the default namespace, with the option of
also being able to explicitly specify ~default as a namespace.

In other words both /ui/dc-1/services/service-name and
/ui/~default/dc-1/services/service-name show the same thing.

This means that if you switch between OSS and Enterprise, all of your
URLs stay the same, but you can still specifically link to the default
namespace itself, and of course link to other namespaces without
changing our URL structure.

Our routing configuration is duplicated in order to achieve this:

- :dc
  - :service
  - :kv
    - :edit
- :nspace
  - :dc
    - :service
    - :kv
      - :edit

Secondly, ember routing resolves/matches routes in the order that you specify
them, unless, its seems, when using wildcard routes, like we do in the
KV area.

When not using the wildcard routes the above routing configuration
resolves/matches a /dc-1/kv/service to the dc.kv.edit route correctly
(dc:dc-1, kv:services), that route having been configured in a higher
priority than the nspace routes.

However when configured with wildcards (required in the KV area), note
the asterisk below:

- :dc
    :service
  - :kv
    - *edit
- :nspace
  - :dc
    - :service
    - :kv
      - *edit

Given something like /dc-1/kv/services the router instead matches the
nspace.dc.service (nspace:dc-1, dc:kv, service:services) route first even
though the dc.kv.edit route should still match first.
Changing the dc.kv.edit route back to use a non-wildcard route
(:edit instead of *edit), returns the router to match the routes in the
correct order.

In order to work around this, we catch any incorrectly matched routes
(those being directed to the nspace Route but not having a ~
character in the nspace parameter), and then recalculate the correct
route name and parameters. Lastly we use this recalculated route to
direct the user/app to the correct route.

This route recalculation requires walking up the route to gather up all of
the required route parameters, and although this feels like something
that could already exist in ember, it doesn't seem to. We had already
done a lot of this work a while ago when implementing our href-mut
helper. This commit therefore repurposes that work slightly and externalizes
it outside of the helper itself into a more usable util so we can import
it where we need it. Tests have been added before refactoring it down
and simplifying it slightly to make the code easier to follow.

The result is a simple function that can be passed easily to anything transition-like:

router.transitionTo(...transitionable(route, potentiallyReplacingParams, owner))
router.replaceWith(...transitionable(route, potentiallyReplacingParams, owner))
// etc

A transitionable being an array with the first element being the name of the route to transition to and all the other elements being the parameter values for the route:

// /:dc/services/:service
['dc.service.show', 'dc-1', 'service-0']

We had also been using this code in another upcoming branch in place of refresh so that we could 'refresh' error pages back to their original route.

route.refresh() // doesn't seem to work if there was an error
///
const route = getOwner(this).lookup('route:${this.router.currentRoute.name});
route.transitionTo(...transitionable(route, {}, getOwner(this))) // works on error pages

As well as obviously using this for our original href-mut helper (just change a single param somewhere in the URL)

Further work potentially on the end of this PR are further moving the nspace specific code out of the transitionable util so that it is no longer project specific, and deciding on whether to require passing the ember owner/container into the util.

[kaxcode]

LGTM