Add `displayId` to `GroupedTaskInfo`

Then in launcher side we can get the `displayId` from the DesktopTask
directly when it is a DesktopTaskView.
Launcher side change can be found at ag/32083183.

Bug: 401011627
Flag: com.android.window.flags.enable_multiple_desktops_frontend
Flag: com.android.window.flags.enable_multiple_desktops_backend
Test: m
Change-Id: I38b86d2b96cfe1fe0cf601d96f1b2a2c41bb7622