[flexiglass] Use SecureTextField for PasswordBouncer

This CL updates PasswordBouncer to migrate from TextField to a SecureTextField so that the password's last character is visible while typing (see TextObfuscationode.RevealLastTyped). With b/416411014 this will also respect the System.TEXT_SHOW_PASSWORD setting then.

SecureTextField uses TextFieldState instead of a value and onValueChange, so I had to make some more changes than initially planned.

I've also updated the tests for other bouncer related views to validate that the onIntentionalUserInput lambda is being called correctly.

Fixes: 418163964
Test: atest PasswordBouncerViewModelTest
Test: atest PinBouncerViewModelTest
Test: atest PatternBouncerViewModelTest
Flag: com.android.systemui.compose_bouncer
Change-Id: Ic8049575bc773f62469b14b94de4841da699b497