Expose TcpRepairWindow as module-lib API

Connectivity service is going to become a mainline module which
will not be able to access hidden APIs. TcpKeepaliveController
is a part of CS mainline module, it uses TcpRepairWindow to
store tcp repair window info. Thus, expose TcpRepairWindow as
module-lib API to support the usage.

Bug: 172183305
Test: atest FrameworksNetTests
Change-Id: I1b6f5ae698f4b6e030a0f776aeafc774fa9f1437