`LIKE` escape sanity:

* Deprecate `like_escape()`
* Add a method to `$wpdb`, `->esc_like()`, and add unit tests

`$wpdb::esc_like()` is not used yet. As such, many unit tests will throw `Unexpected deprecated notice for like_escape`. Subsequent commits will alleviate this.

Props miqrogroove.
See #10041.

Built from https://develop.svn.wordpress.org/trunk@28711


git-svn-id: http://core.svn.wordpress.org/trunk@28527 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Replace all uses of `like_escape()` with `$wpdb->esc_like()`.

Props miqrogroove.
See #10041.

Built from https://develop.svn.wordpress.org/trunk@28712


git-svn-id: http://core.svn.wordpress.org/trunk@28528 1a063a9b-81f0-0310-95a4-ce76da25c4cd