Storage Settings hides categories when loading

To hide sorting animation.

- Storage Settings always loads cache and updates UI, then
  loads storage size and updates UI.
  Remove the chche design because storage category preferences
  will hide during loading, it no meaning to load from cache
  and update UI.

- Hides loading circle before storage category preferences
  become visible, it prevents flickers.

- Remove Calculating... summary of StorageItemPreference.

- Private storage category preferences and secondary user
  preference become visible at
  StorageItemPreferenceController#onLoadFinished.

Bug: 188731179
Bug: 185547228
Bug: 188615591
Test: atest com.android.settings.deviceinfo
      atest com.android.settings.deviceinfo.storage
      make RunSettingsRoboTests -j ROBOTEST_FILTER=com.android.settings.deviceinfo
      make RunSettingsRoboTests -j ROBOTEST_FILTER=com.android.settings.deviceinfo.storage
      manual visual
Change-Id: I3ebef5829ef4f806add07f58fa02520804768be5