This is an ungainly integration with the searchable mixin 😳

I’d prefer for this to be covered by automated tests but
it seems like it only half-works… the placeholder in
the field disappears with the use of keyDown but the
field doesn’t look active. Actually pressing / does
work though.

Has it always been that errors are silently swallowed?
Mysterious

With the expanded try, I found that the reason for search
only working once was that it was required to use set for
these properties, I guess because they’re used by
computed properties.

This is still unwieldly but maybe a bit more sensible now.

I’ve adapted the listener from @DingoEatingFuzz’s keyboard event-
handling here, obviating the need for ember-keyboard:
https://github.com/hashicorp/nomad/pull/8177/files#diff-eb4d61e1e080830b844012c6617c6fa2

The filtering to prevent stealing events from input fields
is adapted from here:
https://stackoverflow.com/a/4171758

This still means a query will be sent for every search, but
if we’re in a route we know has a watched collection, the
cached collection will be used.

Since the container now has align-items: center, this is
no longer needed.

This isn’t perfect as it only updates the last-fetched time
of a watched collection when a search is performed. It also
has the cache duration as 5s which is probably too short.