Long-tap to display Magikeyboard information

**Is your feature request related to a problem? Please describe.**
A fairly common feature for Android apps is to long-tap some input to see what it does when it's not obvious to a user. Currently the keyboard will just use whatever feature the person is trying to find information on, even if they move their finger before releasing. I believe this is against common intuition and can lead to leaking their own information if they're not careful.

**Describe the solution you'd like**
Long-tapping a button should display some concise information on what its purpose is. e.g. "Enter password" is displayed when long-tapping the "***" button.

**Describe alternatives you've considered**
At a minimum, moving one's finger from a button before releasing should cancel the input if possible.

Start by locating the Android keyboard button and input-handling entry points responsible for long taps and movement before release. Compare the current behavior with the requested long-tap information display and cancellation alternative. Done means the intended button information appears without triggering the action, and moving before release cancels input where supported.

Written by the indexing model from the issue text.