Add @RequiresPermission annotation to virtual input device creation binder calls.

This is to avoid the following build warning:

[AndroidFrameworkRequiresPermission] Method createVirtualKeyboard() annotated [none] but too narrow; invokes method requiring {allOf=[android.permission.CREATE_VIRTUAL_DEVICE]}

Bug: 237537306
Test: atest VirtualDeviceManagerServiceTest

Change-Id: I36606da2d58bc4020618060a02193b6d69470c09