Update syncInputWindows to use a callback.

Adds callbacks to InputWindowCommands and updates
SurfaceComposerClient::Transaction::syncInputWindows to use those
callbacks. A subsequent CL will replace syncInputWindows with a method
that adds user defined callbacks to InputWindowCommands. The condition
variable added to SurfaceComposerClient::Transaction is used to retain
syncInputWindows' existing behavior and will be removed once users can
define callbacks.

Bug: b/222421815
Test: manual, TransactionApplicationTest, SwitchImeWindowsFromGestureNavTest
Change-Id: Ib582aded1e42f5e049ebe21d5f2ccedf4cf7d654