SysUiViewModel.hydratedStateOf

Adds hydratedStateOf - a utility to help developers define a "hydrated"
(kept up-to-date) snapshot state (AKA compose State) property with a
single line of code and without needing to add a collector in the
activation code.

Bug: 354269846
Test: unit tests added
Test: manually verified with the next CL
Flag: NONE unused utility (in this CL)
Change-Id: Ibe0ccc623253d6df76cdef5c0842dda381b5a48a