Separate the timeout behavior from PacketRetransmittingState class.

The purpose is to make subclass that only requires timeout method
could extend from TimeoutState instead of PacketRetransmittingState,
avoiding the anti-pattern of using inheritance for code reuse only.

After refactoring, class inheritance relationship looks like:

LoggingState <-- TimeoutState <-- PacketRetransmittingState <-- DhcpInitState

Bug: 140223017
Test: atest FrameworksNetTests NetworkStackTests
Test: atest NetworkStackIntegrationTests

Change-Id: I1fed3ff3ef8b0bdf3645188949e38c3a332f9d6e