Database: Restore numbered placeholders in `wpdb::prepare()`.

[41496] removed support for numbered placeholders in queries send through `wpdb::prepare()`, which, despite being undocumented, were quite commonly used.

This change restores support for numbered placeholders (as well as a subset of placeholder formatting), while also adding extra checks to ensure the correct number of arguments are being passed to `wpdb::prepare()`, given the number of placeholders.

See #41925.


Built from https://develop.svn.wordpress.org/trunk@42056


git-svn-id: https://core.svn.wordpress.org/trunk@41885 1a063a9b-81f0-0310-95a4-ce76da25c4cd