iPads have never had any official support from Apple for displaying battery health to the user. However, all that is "under the hood" and can be accessed by Apple via an official diagnostic test. I've gotten a few when I brought my iPads in for service at an Apple Store. It might also be possible to do it with an Apple remote diagnostic.
There are some tools that might be able to give you an estimate. The one I use is coconutBattery for Mac, which is an unofficial tool that accesses the "under the hood" info. There is an app (available from the App Store) called Battery Life that used to display something similar, but they lost official access from Apple to all the internal stuff. A newer version is still available, but it only estimates battery health by monitoring the battery with the user running it completely down.