Creates a BootCompleteCache

This cache is set by SystemUIApplication on boot and can be queried or
subscribed to.

The cache registration turns into no-op after boot, returning the boot
state instead.

LocationControllerImpl uses this cache to determine if it can query
LocationManager

Test: atest BootCompleteCacheTest
Fixes: 145019350
Change-Id: I2e34e53bfb8beca730cec8da6125988554c659e4