Use wp_cache_get_multiple in fill_descendants

[spacedmonkey]

In the fill_descendants method in WP_Comment_Query, there is a loop the calls wp_cache_get. Instead of getting one key at a time, use wp_cache_get_multiple and get all keys at once.

Trac ticket: https://core.trac.wordpress.org/ticket/57803

[spacedmonkey]

Before

[spacedmonkey]

After

LGTM 👍

[spacedmonkey]

Making this as commit, as this PR as been approved by too long term contributors, @tillkruess @mukesh27. Will commit by the end of the week.

[spacedmonkey]

In 55607:

Comments: Use wp_cache_get_multiple in WP_Comment_Query.

In the fill_descendants method in WP_Comment_Query, there is a loop the calls wp_cache_get to get child comments. Instead of getting one key at a time, use wp_cache_get_multiple` and get all keys at once.

Props spacedmonkey, tillkruess, mukesh27.
Fixes #57803.

Committed.

[spacedmonkey]

Dev note: ​https://make.wordpress.org/core/2023/07/17/improvements-to-the-cache-api-in-wordpress-6-3/