[sb] get rid of recomposition on the StatusBarRoot

StatusBarRoot was using AndroidView, and a single top-level `visible`
flow to determine whether or not to hide the entirety of
PhoneStatusBarView.

This was ultimately pretty inefficient, and was not what the previous
fragment was doing. This change does two main things:

1. Use the HomeStatusBarViewBinder to set initial visibilities to GONE,
   and relies on the bindings themselves to adjust as-needed
2. Removes the need for the `update` block in the AndroidView that
   contains PhoneStatusBarView

Test: sysui tests
Test: manually kiling sysui
Bug: 393610814
Flag: EXEMPT bugfix
Change-Id: If79b8f20cedeee4ecf19ace69d41f7966cab03f4