Make WeatherStateIcon.fromInt @JvmStatic to use it in java.

See ag/33314663, where it's used in java.

Also switched from `values()` to `entries` for improved performance.

Flag: com.android.systemui.shared.smartspace_ui_update
Bug: 389957594
Test: manual - observe weather icon in weather tomorrow.
Change-Id: Ie6011fa48af81efd7d1cc1a262c206ab972cdeb5