Added direct call to syncInputTransactions

Previously, there was only a way to inject input after syncing inputs.
However, some tests require a direct call to sync inputs since we need
to ensure the info was propagated to InputManager native before
continuing with the test. This exposes a method just to
syncInputTransactions.

Bug: 130695122
Test: ActivityLifecycleTopResumedStateTests
Test: MultiDisplayPolicyTests
Change-Id: Ie3115741a20d04c743fd854ac421dc3705332488