Let's update the SearchInput component to extend glimmer/component
instead of ember/component. Glimmer components offer a bunch of various
advantages over classic components and are the direction that ember is
heading in general.

While we're here, let's also re-enable the eslint rules for which the
SearchInput component had the only violations.

Ember's this.render method and @ember/test-helpers's render method are
equivalent, but using @ember/test-helpers' render method is the
recommended approach. As such, let's go ahead and switch this over.

While we're here, let's re-enable this eslint rule as we no longer have
any violations.

Let's prefer angle bracket syntax to curly syntax when invoking the
SearchInput component in our integration tests.