Server-side logic to support unique IDs in the Interactivity API directives to match what the client is doing (https://github.com/WordPress/gutenberg/pull/72161). Props santosguillamot, darerodz, luisherranz. Fixes #64106. Built from https://develop.svn.wordpress.org/trunk@61020 git-svn-id: http://core.svn.wordpress.org/trunk@60356 1a063a9b-81f0-0310-95a4-ce76da25c4cd