Remove SignalClusterView in favor of IconManager

Refactors SignalClusterView into StatusBarSignalPolicy so that it can be
used in a StatusBarIconContainer and solve all of our status bar
problems.

- Remove all uses of SignalClusterView and references to
  R.id.signal_cluster. The class still exists it's just unused now

- Add StatusBarIconHolder, which can point to StatusBarIcon,
  WifiIconState, or PhoneIconState

- StatusBarIconList.Slot. Allows for easier indexing of icons now that
  there can be multiple icons per slot

- Add StatusBarWifiView to be inflated inside of the
  StatusBarIconController when needed

- StatusBarMobile view. similar to above

- Upgrade StatusBarIconControllerImpl and StatusBarIconList to
  understand the holders and added 2 new methods to specifically handle
  wifi / phone state changes

- Create IStatusBarIconView (todo: rename). Abstracts the properties we
  want away from StatusBarIconView so that we can use an arbitrary view
  type

- NeutralGoodDrawable. Draws a light and a dark icon when needed.

- Fixes a few demo mode bugs: multi sim was broken and also turning off
  demo mode was a little broken

TODO: More tests are needed for StatusBarSignalPolicy and maybe the
IconManagers

Test: runtest systemui; visual
Bug: 63772836
Bug: 73778753
Bug: 74985733
Fixes: 74427768
Fixes: 74338687
Fixes: 74388467

Change-Id: I5621b3013cdc9638b61552bd4d7211f211eddf1b