max_num_pages for WP_User_Query

[birgire]

The WP_User_Query class supports pagination but doesn't have the public max_num_pages property, like most of the other query classes do.

This can be useful when using e.g. paginate_links() and also for better consistency.

[Soean]

Hello @birgire,
thanks for your patch. You can upload the fix and the tests in one file, you don't have to separate it into two files.
Since #41452 you don't have to add the @access notations in the DocBlocks anymore.

[birgire]

Thanks @Soean, I didn't know about the @access change.

I will update the patch accordingly.

[birgire]

Removed @access and combined the patch into a single file.