[Flexiglass] ScrollViewFields gardening

Use @JvmField for ScrollViewFields, because we want to treat these
properties as NSSL's private fields, so why bother with the getters.

Also update ScrollViewFields dumps.

Bug: 417965077
Test: dumpsysui NotificationStackScrollLayout
Flag: com.android.systemui.scene_container
Change-Id: I879c347573c1862b656a34abe69ac5873f76fe25