List Table: Restore the List Table items property to allow Bulk Actions to be properly determined.

This fixes the display of Bulk Actions where there exists only a single page of results.

Props shaneeckert, jobthomas, dd32.
Fixes #45028.

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git-svn-id: https://core.svn.wordpress.org/trunk@43500 1a063a9b-81f0-0310-95a4-ce76da25c4cd