[Stats Refresh] Period Posts and Pages: fix displaying details view

[ScoutHarris]

Ref #11360

This is the first step in fixing #11360. Which is - instead of adding all the data to one UIStackView, use UITableViewCells instead. This change fixes Period > Posts and Pages in that manner.

Previously, all the data was stuffed into the stack view on the TopTotalsCell card. Which didn't work out so well with a lot of data.

Now it only uses the TopTotalsCell card to show the "header" via the new DetailSubtitlesHeaderRow. The stack view is left empty. Instead, a UITableViewCell is added to the table for each data row via the new DetailDataRow.

There should be no visual or functional changes, but showing the details view is a lot faster. To note, there is still no loading view, so there may still be a blank view for a couple seconds for longer periods.

Side note: The constraint warnings are not to do with the details view, but are from the Reader and News Card, and are present on develop as well.

To test:

• Go to Stats > Period > Posts and Pages on a very active site (like en.blog or Hogwarts).
• Select View more.
• Verify the data appears relatively quickly.
• Verify selecting a row displays the Post Stats view.

Update release notes:

• If there are user facing changes, I have added an item to RELEASE-NOTES.txt.

[danielebogo]

LGTM! It worked as expected!