Use ManagedLgIcuCollator on Windows (FWNX-296)

It improves maintainability if we use the same implementation
on Linux and Windows, therefore we use the ManagedLgIcuCollator
on Windows as well and remove the unmanaged implementation of
LgIcuCollator.

Change-Id: I2de8604078818c5c8555ba4ae0a3a01b75344fb0