[Physical Keyboard] Add slow keys dialog

demo: https://screenshot.googleplex.com/7CPpfHvAixe9Awr.png
Add dialog for Slow keys, which have same set up with Bounce keys.
Move dialog logic to InputSettingPreferenceController, to reuse it from
slow keys controller.

Bug: 346949547
Test: atest SettingsRoboTests
Flag: com.android.settings.keyboard.keyboard_and_touchpad_a11y_new_page_enabled

Change-Id: Ia4d74fcf3f20ed68cb252503e88d99ea79eae291