fix and reintroduce topic cards work

[escattone]

We reverted the topic cards work -- see mozilla/kitsune#6495 -- until we can resolve why it makes the home page and the product-landing pages load very slowly. The work for this issue includes fixing the performance issue and re-introducing the work.

[emilghittasv]

This was retested in both dev and stage.

Apart from the same verification which were performed in #2042 (comment) we are no longer seeing performance issues inside the homepage, product landing pages and product solutions pages.

Moving this ticket inside the release column.