Don't request focus on PIN's passwordView unless view is visible

Rather than fixing the bouncer lifecycle issue, manually
check the PIN view is visible before ever requesting focus
on its password entry view.

Test: atest KeyguardPinBasedInputViewControllerTest
Test: manually set pin; then set swipe; then set pin;
press power button to screen off, then to lockscreen;
send keycode events for pin and then enter;
observe device doesn't get unlocked without showing
the bouncer
Bug: 417307529
Flag: com.android.systemui.bouncer_lifecycle_fix

Change-Id: If4d5f2fb13e653adb97eaeaab6a177602da06ccb