[FR] Add PasswordFormBox

**Is your feature request related to a problem? Please describe.**
Now that we have `PasswordBox` (https://github.com/bdlukaa/fluent_ui/pull/795) we do need `PasswordFormBox`, too.

**Describe the solution you'd like**
A `PasswordFormBox` to use with forms.

**Describe alternatives you've considered**
`TextFormBox`+`obscureText: true`

**Additional context**
N/A