logd: remove SocketClient from LogBuffer and LogBufferElement

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
14 files changed
tree: 30a1cd430b63670f148c80262e375be0aaa2d9ec
  1. liblog/
  2. logcat/
  3. logd/
  4. logwrapper/