Frameworks: Move SharedPreferencesImpl to tristate

The code loading shared preferences from disk may throw in other
ways then a missing file, for example during an out-of-memory
situation. Ensure that waiters will be woken up, and propagate
the exception to the getters.

Bug: 67986472
Test: m
Test: Device boots
Test: m cts && cts-tradefed run commandAndExit cts-dev --module CtsContentTestCases -c android.content.cts.SharedPreferencesTest
Change-Id: I56e47342111f1cb53c5817c0429af4a6787475a9