This PR merges the topic-list-item card component into the nextgen theme.
Also does the following cleanup:
* Use template-only ember components
* Use `fire` instead of deprecated `fa-fire` icon
* Lower version requirement for node to 18 to match core
* Add english locale strings for topic status column
* Remove dummy theme settings
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Co-authored-by: Martin Brennan <martin@discourse.org>
David Taylor