General: Use interpolation instead of concatenation for all dynamic hook names.

This fixes the rendering of the hook names on developer.wordpress.org.

Props keesiemeijer
Fixes #39148

Built from https://develop.svn.wordpress.org/trunk@39600


git-svn-id: https://core.svn.wordpress.org/trunk@39540 1a063a9b-81f0-0310-95a4-ce76da25c4cd