The app's wrapper element ID is different in tests. `app.rootElement` allows us to consistently obtain the selector in the initializer, so it works correctly regardless of the app's configuration.
And also move all the "top topics by period" routes to query string param.
/top/monthly => /top?period=monthly
/c/:slug/:id/l/top/monthly => /c/:slug/:id/l/top?period=monthly
/tag/:slug/l/top/daily => /tag/:slug/l/top?period=daily (new)
This moves the "This site was just updated" modal asking the user if they want to refresh into a subtle prompt that slides down from the header.
Also in this PR I've added a helper to publish message bus messages in JS tests. So instead of this:
```javascript
// Mimic a messagebus message
MessageBus.callbacks
.filterBy("channel", "/global/asset-version")
.map((c) => c.func("somenewversion"));
```
We can have:
```javascript
publishToMessageBus("/global/asset-version", "somenewversion");
```
Using arrow functions changes `this` context, which is undesired in tests, e.g. it makes it impossible to setup things like pretender (`this.server`) in `beforeEach` hooks.
Ember guides always use classic functions in examples (e.g. https://guides.emberjs.com/release/testing/test-types/), and that's what it uses in its own test suite, as do various addons and ember apps.
It was also already used in Discourse where `this` was required. Moving forward, it will be needed in more places as we migrate toward ember-cli.
(I might later add a custom rule to eslint-discourse-ember to enforce this)
In newer Embers jQuery is removed. There is a `find` but it only returns
one element and not a jQuery selector. This patch migrates our code to a
new helper `queryAll` which allows us to remove the global.
We used many global functions to handle tests when they should be
imported like other libraries in our application. This also gets us
closer to the way Ember CLI prefers our tests to be laid out.
This is where they should be as far as ember is concerned. Note this is
a huge commit and we should be really careful everything continues to
work properly.
