Add keyboard input support for the PIN bouncer

Bug: 338969289
Flag: com.android.systemui.scene_container
Test: atest PinBouncerViewModelTest
Test: manually,
    go to the PIN Bouncer
    run adb shell input text "PIN_DIGITS"
    run adb shell input keyevent ENTER
    bouncer should get dismissed
Change-Id: Ie836afcd36fa1530d9957a6b061ec76f9e55b60d