Follow-up improvements to zen mode icon picker

* Propose icons from com.android.internal.R instead of android.R (as a proof of concept) since this is what we'll be doing with the final icons.
* Provide the icon options as a parameter to the controller (can also be used for testing).
* Fix some Lint warnings.

Test: atest ZenModeIconPickerListPreferenceControllerTest
Bug: 333901673
Flag: android.app.modes_ui
Change-Id: I023eed0fd5719c5c4540f8d145335f60d088e7fb