Reimplement android.os.SystemProperties in terms of libc facilities

A subsequent CL will implement a new prop_info based properties API on
top of this CL.

Test: boots
Test: atest FrameworksCoreSystemPropertiesTests
Bug: 140788621
Change-Id: Id8dd02fff7b1c0815a27ab1dfdde1700447a414c
2 files changed