Comment statistics for node search rankings should aggregate all comment fields

Problem/Motivation

In CommentStatistics::getRankingInfo(), the search ranking for comment count is based on the count for specifically the default 'comment' field for nodes.

But now admins can add different comment fields to node types. So we should really be aggregating the count over all fields.

Steps to reproduce

Proposed resolution

Here's the current code:

'join' => [
  'type' => 'LEFT',
  'table' => 'comment_entity_statistics',
  'alias' => 'ces',
  // Default to comment field as this is the most common use case for
  // nodes.
  'on' => "ces.entity_id = i.sid AND ces.entity_type = 'node' AND ces.field_name = 'comment'",
],
...
'score' => '2.0 - 2.0 / (1.0 + ces.comment_count * (ROUND(:comment_scale, 4)))',

What needs to happen is that in the join, we wouldn't restrict to ces.field_name = 'comment', and in the score, we would do a SUM(ces.comment_count).

This would require some kind of a group by, which I don't think hook_ranking() supports right now.

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet