[FEATURE] Hide password confirmation when password is unobfuscated

[otto-dev]

There is little purpose to the "Confirm Password" input when the password field is displayed in plain-text. It's too expensive from a UX perspective to force the user to repeat the password if they can already see what they typed.

It would be nice if the password confirmation field is automatically removed from the screen and validation logic when the user clicks the un-obfuscation icon.

The password visibility icon should then only be displayed on the main password input.

Somewhat related: https://github.com/NearHuscarl/flutter_login/issues/367