In the future, we'll want to be able to write to outputs that are not
necessarily a libsysutils SocketClient, for example host tests of
LogBuffer. Therefore, we add a LogWriter class to be used instead of
SocketClient.
Test: logging unit tests
Change-Id: I4385be65e14e83a635691a7ba79e9bf060e49484
We may use different implementations of LogBuffer in the future, so we
make it interface and create a concrete ChattyLogBuffer class that
implements it.
Test: logging unit tests
Change-Id: I5731d6404640664c9acc26b7c677dff3110c6a11