Window Manager Flag Migration (9/n)

Update the leash of InsetsSourceControl and send it to the client while
the insets source window is moved.

This CL also guarantees that the array of InsetsSourceControl send to
the client side doesn't contain any null element.

Bug: 118118435
Test: atest InsetsSourceProviderTest InsetsStateControllerTest
            InsetsPolicyTest WindowStateTests CommandQueueTest
            RegisterStatusBarResultTest InsetsFlagsTest
            LightBarControllerTest RegisterStatusBarResultTest
            ViewRootImplTest DisplayPolicyLayoutTests
            DisplayPolicyInsetsTests DisplayPolicyTests
            TaskSnapshotSurfaceTest NavigationBarColorTest
Test: Rotate Camera in the new insets mode

Change-Id: I96d7ac5c37abbb472dab4cd2c24644e136d23947