Posts, Post Types: Add a parameter to the `post_locked_dialog` action which...

Posts, Post Types: Add a parameter to the `post_locked_dialog` action which contains a reference to the user who holds the lock.

Fixes #48443
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git-svn-id: https://core.svn.wordpress.org/trunk@47006 1a063a9b-81f0-0310-95a4-ce76da25c4cd